On the Concept of Real Use of Reason

1 Introduction. Wavering interpretations of the concept of usus realis

In the opening pages of the Transcendental Dialectic, Kant distinguishes between logical and real use of reason.^[1] In its logical use, reason is a faculty “for imposing on given modes of knowledge a certain form, called logical – a faculty through which what is known by means of the understanding is determined in its interrelations, lower rules being brought under higher.” That is the logical use of reason as “the faculty of making mediate inferences.”^[2] These inferences consist in subsuming cognitions under universal conditions (the premises of syllogisms) wherefrom those cognitions are deduced.^[3] In turn, the premises of the syllogism should be grounded in more general principles^[4] following a course that leads to subsumption of all cognitions under a first universal premise. “[R]eason, in its logical employment, seeks to discover the universal condition of its judgment (the conclusion).”^[5] This activity of systematic organization of the cognitions of understanding is an operation that cannot be performed by the understanding itself. Instead, it originates in the nature of reason and in reason’s demands, as Kant explains in the passage of KrV A305/B362:

As a matter of fact, multiplicity of rules and unity of principles is a demand of reason, for the purpose of bringing the understanding into thoroughgoing accordance with itself.^[6]

To comply with this demand, reason generates ideas and principles which serve as unifying norms of the aggregate of cognitions gathered by understanding. This is the real use of reason. That is why reason is defined in KrV A299/B356, as the faculty of the principles. These principles are not applied to objects but solely to the cognitions and rules of the understanding. “[S]uch a principle does not prescribe any law for objects …; it is merely a subjective law for the orderly management of the possessions of our understanding, that by comparison of its concepts it may reduce them to the smallest possible number.”^[7]

Kant provides enough indications concerning the meaning of the concept of real use of reason.^[8] Heimsoeth has offered an adequate interpretation, although not entirely determined; he explained that this use of reason, in contrast with the logical use, is endowed with a content of its own. He characterized the real use as “sachhaltig”: “The logical use of reason should be distinguished from the real one, which has a content.”^[9] But that would then allow a possibility of understanding such content as a real object, or as a thing in itself, whereas reason would be directed; so that the real use of reason would then be (mistakenly) taken as a rash assertion of reason about phenomenal things or about things in themselves. Instead, in the present article we suggest that the content of the real use of reason is just an idea or principle generated by reason itself.

As a consequence of the abovementioned ambiguity of Kant’s explanation, most interpreters explain the real use of reason in connection with objects. For instance, Zöller seems to identify the real use of reason “with the objective, real givenness of the inferred unconditioned.”^[10] In addition, Klimmek states that “a real use of reason takes place when the demand of reason in its logical use, to pursue ‘unity of principles’ … is taken at the side of ‘the object itself’.” Real use of reason no longer seeks the systematic unity of laws and cognitions of the understanding (as in the case of the logical use) “but [a kind of unity] of the objects themselves.”^[11]

According to Willaschek, real use of reason is characterized by its reference to things. It is “the use of pure reason specific to metaphysics.”^[12] He states that it “consists in drawing rational inferences from a priori premises (e.g., the paralogisms and the proofs of the antinomies).”^[13] Performing its real use, reason moves “from mere logical conditioning relations among cognitions to ‘real’ conditioning relations among things.”^[14] On further development of the concept of usus realis Willaschek distinguishes two ways of conceiving it: either we take the real use of reason as reason’s wholly illegitimate reference to the objects of its ideas, or else as a legitimate reference of reason to a just “putative” object.^[15]

In both cases, he understands the real use as being a reference reason bears to objects, be these taken as the objects of a realistic metaphysics, or as just hypothetical suppositions. In his own words, he states:

While the logical use of reason consists in drawing inferences, the validity of which depends only on their form, the real use of reason consists in gaining a priori cognitions about conditioning relations among objects (which objects are the matter of our cognitions). … On the one hand, the real use of reason will typically consist in drawing rational inferences from a priori premises (e.g., the paralogisms and the proofs of the antinomies). On the other hand, the cognitions on which the logical use of reason operates (in order to unify them into a coherent and complete system) will include the a priori cognitions (or putative cognitions) provided by the real use of reason.^[16]

Thus, according to these widely spread interpretations, the real use of reason would be nothing but an illegitimate use of reason. We will attempt to demonstrate that such an interpretation of the real use of reason (which considers it as its use with reference to objects) fails to be adequate.

Furthermore, Kraus offers an explanation of the real use of reason that seems rather to fit with the regulative or with the transcendental use of it, as she writes: “reason’s real use concerns the specific “object [of] reason”, namely the understanding …. [R]eason’s real, regulative use consists … in directing the understanding towards a good use and that is, more specifically, in determining the limits of experience.”^[17] Similarly, Licht dos Santos states that the concepts produced through the real use of understanding (and presumably also of reason) bear no reference to objects, neither sensible nor supersensible, but they are “only a mere conceptual and abstract representation of the intelligible world.”^[18]

In my view, the real use of reason does not reach in any case beyond the generation of ideas and principles. It has no reference to objects. Reference to objects is a further step which is not performed by the real use of reason, but by the product of that use: namely by the ideas. That is why ideas require a deduction in order to establish the legitimacy of their reference to objects.

2 The explanations of the real use of reason in the Critique of Pure Reason

We need to call to mind the texts of the Critique where Kant refers to this real use.

In one of these texts Kant presents real use as a possible use of reason where this would be “an independent source of concepts and judgments which spring from it alone, and by means of which it relates to objects.”^[19] It is to be noted that this characterization of the real use of reason contains two parts: according to the first, reason is the source of concepts and judgments; according to the second part, reason makes use of those concepts and judgments generated by reason itself to refer to objects.^[20]

Let us now consider another passage where the concept we wish to study is further determined. It is the passage of KrV A299/B355, which states: “Reason, like understanding, can be employed in a merely formal, that is, logical manner, wherein it abstracts from all content of knowledge. But it is also capable of a real use, since it contains within itself the source of certain concepts and principles, which it does not borrow either from the senses or from the understanding.” No mention of objects is made here: real use is defined only by the concepts and principles generated by reason. It is these which constitute the content alluded to by Heimsoeth in the abovementioned passage.

Our task in the present article consists in referring to the first part of the mentioned passage KrV A305/B362, as well as to the definition of real use in KrV A299/B355, where there is no mention of any claim of validity for real objects.

3 Parallelism with understanding whose own spontaneous synthetic activity produces the categories as concepts

In its real use as described and defined, reason reveals a parallelism with understanding. In the nature of the latter, there is, also, a repertory of spontaneous actions (codified in the table of judgments according to formal logic). There is also a repertory of pure concepts of understanding derived from those actions. Hence, there is a real use of understanding.^[21] In the production of ideas (i.e., in its real use), reason proceeds in the same manner used by understanding when producing categories. Therefore, it takes into account only those actions which constitute its own nature.

The stated real use of understanding required, as is well known, a transcendental deduction in order to demonstrate that such pure concepts of understanding are not empty creatures of thought, without any actual relation to objects. Objective validity (i.e., relation to objects) of pure concepts demanded, in the Analytic, a demonstration through a specific operation, once real use of understanding had produced such concepts. Thus, it is possible to conceive of the production of pure concepts independently from their application to objects. Application requires a specific deduction. The same exigence appears when considering not just the understanding but reason and its real use: reason in its real use produces concepts (ideas). Objective validity of those concepts (their reference to objects) must be demonstrated through an additional operation, different from the mere production of them. This demonstration is a further step which follows the mere generation of concepts by reason. Real use of reason consists only in this spontaneous generation of concepts (ideas) and principles. Demonstration of the existence – or else of nonexistence – of that which is thought in those concepts (ideas) requires a further step, different from the mere generation of them. Wolff has already insisted on this topic.^[22]

4 Real use of understanding in MSI

The stated real use of understanding becomes apparent in paragraphs 5, 6 and 23 of the 1770 Dissertation. It is well to heed this exposition, since it offers a clear explanation of what should be understood by usus realis and by usus logicus. In this essay, Kant still refers to the “superior faculty of the soul” as “intellect” and distinguishes two uses of the intellect: “ante omnia probe notandum est, usum intellectus s. superioris animae facultatis esse duplicem: quorum priori dantur conceptus ipsi vel rerum vel respectuum, qui est usus realis; posteriori autem undecunque dati sibi tantum subordinantur, inferiores nempe superioribus (notis communibus) et conferuntur inter se secundum princ. contrad., qui usus dicitur logicus .”^[23] By means of the real use of the intellect, presented there, certain concepts are given (are produced); these are concepts of things or of relations.^[24] However, they do not originate in the knowledge of such things or relations. Instead, those concepts “are given by the nature of the intellect itself.”^[25] (It is to be noted that until after 1770 Kant admits the coincidence of the laws of thought and the laws of things.)^[26]

Shortly after the publication of this work, Kant himself realized that the objective validity of those pure concepts (their legitimacy as regards their reference to things) had not yet been satisfactorily demonstrated (as may be read in the well-known letter to Marcus Herz, of February 21, 1772), so that from the explanation of those concepts in MSI there remains in the Critique only the admission that the understanding produces them spontaneously. Their reference to objects is quite a different issue, which requires further demonstration.

5 According to its own nature, reason is the source of ideas and principles

Reason, according to its own nature, produces concepts (ideas) and principles. In KrV A299/B356, reason is defined as the faculty of the principles. The faculty of the principles establishes the “unconditioned synthetic unity of all conditions in general.”^[27] This rational unity is conceived of in the ideas of reason. The establishment of the legitimacy of the principle of synthetic unity demands a specific deduction.

6 Reason as the source of principles

In the Logic, a principle is defined as a judgment that is a priori certain, from which other judgments can be inferred, whereas it is not itself subordinate to any other judgment of a higher rank.^[28] A rational principle can be expressed only through concepts; i.e., what makes it different from axioms, which are principles that can be known by intuition.^[29] In the Critique of Pure Reason “knowledge from principles is, therefore, that knowledge alone in which I apprehend the particular in the universal through concepts.”^[30]

Reason is defined as “the faculty which secures the unity of the rules of understanding under principles.”^[31] According to it, reason subsumes actual cognitions of understanding under their conditions and again under the conditions of the conditions, aiming at organizing them in a system depending upon a single universal principle.^[32] This single universal principle is produced by reason itself. It must be supposed by reason, so that it can obey its maxim of finding “for the conditioned knowledge obtained through the understanding the unconditioned whereby its unity is brought to completion.”^[33]

To carry out this transcendental–logical task reason produces, in real use, a principle whose cogency extends not just over formal logical premises but over the actually given cognitions of the understanding. This principle states that “if the conditioned is given, the whole series of conditions, subordinated to one another – a series which is therefore itself unconditioned – is likewise given, i.e., is contained in the object and its connection.”^[34] The said principle refers to the unconditioned, since it means that if the conditioned is given, there should be given also the unconditioned. Let us refer to it as the “Principle” (with capital letter). I would like to call this Principle “transcendental”^[35] insofar as reason does not deal immediately with objects, but with the knowledge of them.^[36] It just presupposes a priori the possibility of a systematic unity without taking this unity as actually given in nature.

Guided by this Principle, reason gives to the activity of understanding goals that allow the consistency among all cognitions and the building of a unitary system of them. The concepts of these goals are the ideas. That is how reason, exercising its real use, produces a Principle that regulates the work of understanding. The produced unity of the multifarious cognitions of understanding is a collective one;^[37] each one of the cognitions embraced in that unity preserves its peculiar features; none of the said cognitions loses them by being submitted to abstraction. To explain this point, Kant has recourse to the distinction between “universality” (complete logical synthesis) and “totality” (completeness of the synthesis of a sensible whole). The absolute entirety of the unity produced by reason by means of a complete logical synthesis is referred to by Kant as “universality,” whereas the absolute entirety of the unity produced by reason by means of a transcendental synthesis carried out upon a whole of cognitions is called “totality.”^[38]

Certainly, the maxim of reason does not command to positively state the unconditioned, but just to search for it. Proceeding according to the maxim under the guide of the Principle does not produce an illegitimate dialectic assertion (although it could be interpreted as such, depending on the meaning assigned to the second “given,” as we shall presently see). It just maintains that everything that is conditioned depends upon its conditions.^[39] Thus, the Principle remains undetermined concerning the first and absolute condition of everything that is given as conditioned. Kant explains this by stating that “the principle of such systematic unity is so far also objective, but in an indeterminate manner (principium vagum).”^[40] Certainly, the Principle refers to actually given cognitions and objects which are one and all conditioned; but it does not take upon itself the formulation of the first and all embracing unconditioned condition in any determinate manner.

7 How the “whole series of conditions” is given

Kant distinguishes two senses of “given,” both of them employed in the formula of the Principle, namely: something may be “really” given as an object for knowing, or else it may be given “as a task” (“aufgegeben”). When setting forth the Principle, he states: “it is evident beyond all possibility of doubt, that if the conditioned is given, a regress in the series of all its conditions is sets us as a task.”^[41] He explains:

if the conditioned as well as its condition are things in themselves, then upon the former being given, the regress to the latter is not only set as a task, but therewith already really given. And since this holds of all members of the series, the complete series of the conditions, and therefore the unconditioned, is given therewith, or rather is presupposed in view of the fact that the conditioned, which is only possible through the complete series, is given.^[42]

Following Kant, Willaschek points out that the assertion contained in the Principle (which states that the unconditioned should be given) should not be exclusively interpreted as if it said that the unconditioned should be given in sensibility, so that it were “made cognitively accessible to a finite epistemic subject”; but that the said Principle should rather be understood as if it indicated that there must be something unconditioned, uncognizable to us, that serves as the ultimate ground of the conditioned.^[43] The unconditioned is required by reason as an indeterminate necessary assumption,^[44] not as something actually given in a possible experience.

We may conclude that the real use of reason that leads to the production of the Principle does not infringe upon the limits the Critique has drawn to the legitimacy of knowledge.

Now, if the unconditioned is given “as a task,”^[45] then it must be conceived of in some way or other. As a matter of fact, it is conceived of as an object in the idea. We shall come to this concept later on.

8 Reason as the source of ideas

Ideas “are just as intrinsic to the nature of reason as are the former [that is, the categories, MC] to that of the understanding.”^[46]

Ideas are not contained in reason as static contents, but they are actively produced by reason. This production is precisely what real use of reason consists of.^[47] As in the case of the concepts of the understanding (which are discovered following the guiding thread of the logical table of judgments). In addition, ideas are found by tracing them through the formal logical use of reason (in the use of reason in syllogisms and the combinations of them). Kant states it as a program at the beginning of the transcendental Dialectic: “we may presume that the form of syllogisms, when applied to the synthetic unity of intuitions under the direction of the categories, will contain the origin of special a priori concepts, which we may call pure concepts of reason, or transcendental ideas.”^[48]

9 Reason’s formal logical way of producing ideas

Kant admits three basic forms of syllogism, in accordance with the three forms of relation listed on the table of judgments: categorical, hypothetical and disjunctive syllogisms. Starting from these logical forms, reason makes an attempt to achieve the unconditioned. It proceeds by progressively moving backward by way of prosyllogisms toward the conditions of the logical conclusion of the syllogism which is taken as the starting point of the regress.

The major premise (which is the condition of the conclusion) “is itself subject to the same requirement of reason, and the condition of the condition must therefore be sought (by means of a prosyllogism) whenever practicable.”^[49] This major premise is itself the conclusion of a previous syllogism. The major premise of that previous syllogism is, in turn, also, the conclusion of a prior syllogism and so does reason successively draw backward, in its logical use, toward the conditions of the conditions. In a second moment, this concatenation is submitted to the principle of reason, which prescribes to find the unconditioned synthetic unity of all conditions.^[50] Therefore, reason obeys its connatural maxim (in its logical use), which demands to seek for “the universal condition” of the conclusion of its inferences. This universal condition is sought for through subsumption of each particular condition (i.e., of each major premise) under another premise of greater universality.^[51] This progression (or regression to prior conditions) by means of the chain of prosyllogisms is the logical form of the procedure of reason, in its real use, to produce ideas. The text of the Critique of Pure Reason explains it in the following way: “that very function of which it [reason, MC] makes use in categorical syllogisms,” does necessarily lead one to conceive of the thinking subject as a substance; “the logical procedure used in hypothetical syllogisms leads to the idea of the completely unconditioned in a series of given conditions, and finally … the mere form of the disjunctive syllogism must necessarily involve the highest concept of reason, that of a being of all beings – a thought which, at first sight, seems utterly paradoxical.”^[52] In summation, logical use of reason, in compliance with the maxim of reason, leads to real use of it, through which it produces ideas.

Kant does not develop along the text these indications (that we might call instructions for the “metaphysical deduction of ideas”). Interpreters have put forward several objections and some of them have even absolutely rejected this Kantian explanation.^[53] We will confine ourselves to offer an answer to the objection put forth by Heimsoeth and supported by Oberhausen as regards the deduction of the idea of God by means of a disjunctive prosyllogism.^[54] Heimsoeth points out that in the abovementioned passage “we cannot easily discover that Kant might have alluded to the idea of God, on the grounds of formal use” of reason.^[55] Similarly, Oberhausen questions the possibility of finding the ideas of the special metaphysics in this deduction.^[56] On the other hand, Klimmek follows Kant’s hint in KrV A321/B378 and points at the logical use of reason as at a “guiding thread” for the discovery of its real use.^[57] We will now try to show the possibility that real use of reason may produce the idea of God through the logical way of the disjunctive syllogism.

10 An example of the real use of reason: The generation of the idea of God by means of the disjunctive syllogism

If we adopt the notation which indicates that A(x) means that something “x” receives the A determination (and analogously B(x), C(x), etc. indicate that x receives the “B,” “C,” etc. determinations), the disjunctive syllogism can be formalized as:

Either A(x) or else B(x) (major premise, proposition major);

but it is not: A(x) (minor premise, minor);

then: B(x) (conclusion).

Which in ordinary language would stand for:

Either x has the A property, or else x has the B property

But it does not have the A property

Therefore x has the B property

Let us now take this so formalized syllogism as a starting point. We will call this first step “Syllogism 1.”

If we apply the prosyllogistic retrogression, we find that the major premise of Syllogism 1 is the conclusion of a previous syllogism. We will call this second step “Syllogism 2.” The premises of Syllogism 2 are the conditions of the major premise of Syllogism 1 (the syllogism we have taken as the starting point).

Syllogism 2

Either C(x), or else [either A(x), or B(x)];

but it is not: C(x)

then: either A(x), or B(x)

As we know, the proposition between brackets: “either A(x), or B(x)” is the major premise of Syllogism 1.

In its turn (and as pointed out by Kant^[58]), the major premise of this new syllogism (of Syllogism 2) arrived at through the second step of prosyllogistic retrogression (the premise that states “Either C(x), or else [either A(x), or B(x)]”) should be regarded as the rational outcome (the conclusion) of a previous disjunctive syllogism, to which we come through a third step. This syllogism would be:

(third step) Syllogism 3

Either D(x) or else {either C(x) or [A(x) or B(x)]};

But it is not: D(x)

Then: either C(x) or [A(x), or B(x)]

where the proposition between the braces “{“and”}” “{either C(x) or [A(x) or B(x)]}” is the major premise of the foregoing Syllogism 2.

In its backward course, this prosyllogistic ascent goes over the conditions of the conditions … (the conditions of the major premises) of each one of the disjunctive syllogisms belonging to the series. The aim of this operation is to attain an absolutely first major premise containing the complete disjunction of all possible major premises. The said absolutely first premise will be an absolute principle, since from it all major premises of the syllogisms leading to it can be deduced. Since the disjunctions concern predicates of x, the complete disjunction would be that of all positive predicates that can be assigned to x. Thus, the concept of x would have the logical form of a realissimum: a concept to which all possible positive predicates belong. Now we have no other way of conceiving of the realissimum, but through the synthesis by means of the categories (thus we conceive it as an object, that is, we must conceive of it as if it were an actual being: an ens). Therefore, we achieve the concept of the Ens realissimum, that is, the concept of God.

A similar prosyllogistic procedure applies as regards the other two ideas. Thus, the logical framing of the idea of world through the hypothetical prosyllogism yields a major premise which is a hypothetical judgment that contains the complete (universal) network of all conditions mentioned in all possible major premises of hypothetical syllogisms. Similarly, the categorical prosyllogism ends in an absolutely first categorical judgment whose subject serves as a subject of all possible predicates though not being itself a predicate.

11 Transcendental Ideas produced by the transcendental–logical real use of reason

On performing the logical exercise of prosyllogistic retrogression, it is possible to conceive of that retrogression as if it were already accomplished, and the universal premise containing all the determinations of x (i.e., containing all the logical conditions of that first inference) had been reached. This assumption is a subjective need of reason, since reason needs “the assumption that all the members of the series on the side of the conditions are given (totality in the series of the premises); only on this assumption is the judgment before us possible a priori.”^[59]

As we have already seen, to this logical universality would correspond, in the employment of reason upon understanding, the totality of the conditions of a given object as well as the compatibility^[60] of all actual conditions and determinations of the given objects.^[61] This is also just reason’s subjective (although unavoidable) assumption. On presupposing this totality (expressed in the abovementioned Principle), reason produces not just a universal major premise, but an idea. The idea guides the activity of understanding along the progress of knowledge. Thus, the Principle reveals itself as being necessary for the ideas of reason to accomplish their regulative function. Nevertheless, the Principle does not assert anything a priori about the actual totality of appearances; it is just a necessary supposition that reason produces according to the maxim which expresses its own essence. The thought of this already accomplished retrogression is conceived as the goal toward which all the activity of understanding is aimed at, led by reason’s maxim of finding the unconditioned.

12 The real use of reason produces an object in the idea

Paraphrasing a passage of the Analytic referred to understanding,^[62] we may say that the same reason, through the same operations by which in formal logical use it produces a chain of prosyllogisms in order to reach unconditioned universal premises, also introduces a content in its ideas through the synthetic unity of the presupposed totality of the cognitions of the understanding. Such content is called an “object in the idea.”

In order to better understand the meaning of the expression “object in the idea” it might be useful to get a glimpse of its history. We will see that the historical approach unexpectedly confronts us with a meaning of the expresssions “object” and “objective” that is the very opposite of the significance we currently give to those terms. Although the genealogy of the question goes as far back as to Duns Scotus and his followers^[63] or even beyond,^[64] it will be sufficient for our purposes to examine it at its stage at the beginning of the early modern philosophy. The expression is in use in the late Renaissance, for instance, in the Disputationes metaphysicae by Francisco Suárez (1597). In the Disputatio LIV, first section, number 5, Suárez distinguishes a sense of the expression esse in ratione according to which something is in reason in the manner of an object. In the first section, number 9, he explains this as he states: “being objectively just in reason is not properly to be, but it means being thought or imagined.”^[65] In the same sense he states that an ens rationis does not properly have a being other than being in the mind.^[66]

The same meaning of objectively being as existence merely in the mind is to be found in Descartes, Meditations, III. He states: “Undoubtedly, ideas that represent substances … contain more objective reality than those which represent just modes or accidents.”^[67] Descartes employs this concept in his demonstration of the existence of God.^[68] Both Suárez and Descartes distinguish objective reality (which exists just as a reality represented in a concept) from its complementary opposite formal reality, i.e., from the actuality of the represented thing itself. To summarize: in any representation of something, the reality of such something is represented as an element of the whole representation. This is the represented reality, or objective reality.

At about the beginning of the eighteenth century the expression “objective” underwent a change in its meaning.^[69] For the authors of the Middle Ages and of the Renaissance it signified that which is but a content of the mind (as opposed to what pertains to things themselves).^[70] For later writers, the phrase takes the very opposite significance; it means that which belongs to the perceived thing, as distinguished from what is just subjective and is inherent in the subject. Both meanings of “objective” coexisted for a long time.

13 The concept of object in the idea in the Dialectic of the Critique of Pure Reason

Kant explains the concept of object in the idea in KrV B698. In his explanation, we find an echo of the ancient sense of realitas objectiva which we have found in Suárez and in Descartes. In the mentioned passage of B 698 Kant states:

There is a great difference between something being given to my reason as an object absolutely, or merely as an object in the idea. In the former case our concepts are employed to determine the object; in the latter case there is in fact only a schema for which no object, not even a hypothetical one, is directly given, and which only enables us to represent to ourselves other objects in an indirect manner, namely in their systematic unity, by means of their relation to this idea.

Ideas are concepts of reason that have the characteristic features of unity and totality. It should be noted that a particular idea is not just a general form: it is also its distinctive content. Properly speaking, an idea does not refer to an object in the idea (as if this one were something different to the idea itself) but it contains that object. The fact of being contained in an idea constitutes all the being of this peculiar object, which has no separate existence. A particular idea is the thought of something in general, conceived of according to the particular kind of synthesis (either categorical, hypothetical or disjunctive), which has given rise to that particular idea. Thus, the use of reason by which it produces an idea is the very same action by which reason produces an object in the idea. The real use of reason may be identified with the generation of a particular kind of object: the object in the idea.^[71]

It may be asked why we should conceive of this content of the idea as if it were an object. A possible answer is that if applied to the cognitions of understanding, ideas would aim at synthesizing that content in the form of a complete (total) unity. Synthesis, in turn, cannot be performed otherwise than in accordance with the categories, which are “concepts of an object in general.” Therefore, the real use of reason consists in producing the concepts of the total achievement of reason’s transcendental operation following the guide of the Principle. In accordance with the categories that rule this synthesis, such concepts turn out to be: firstly (category of “Community”), that of an object which would possess the totality of possible positive determinations (i.e., the totality of the realities) which understanding could possibly know by its investigation of nature; secondly (category of “Causality and Dependence”), the concept of the totality of the conditions that understanding could possibly know by its activity of causally connecting appearances; thirdly (category of “Inherence and Subsistence”), the concept of a subject in which the totality of predicates are inherent, not being itself a predicate. These concepts of totalities are the products of real use of reason. Being framed through a categorical synthesis, these totalities can but have the form of objects (since they can be synthesized and conceived of only by means of the categories).^[72] Thus, they turn to be the ideas of God, of the World and of the Soul. These objects are thought of as if they were real objects, whereas they are objects whose reality consists in being thought: they are objects in the idea. The generation of such objects in the idea is not a deception. The hypostasis (substantialization) of them has not yet taken place.

14 The function of the object in the idea in the legitimate use of reason

The supposition of the object in the idea (not the metaphysical assertion of an object of the idea) is a necessary supposition, since “reason cannot think this systematic unity otherwise than by giving to the idea of this unity an object.”^[73] The object in the idea performs the function of a kind of schema. As a schema produced by reason, the object in the idea mediates between sensible things and intelligible world, just as the schemata of the categories mediate between sensible appearances and pure concepts of understanding.

By following the guide of reason that leads understanding’s enquiries towards the goal of absolute completeness and thus presupposes that all partial understanding’s enquiries would be encompassed within these just thought and presupposed objects in the idea, understanding proceeds as if all its cognitions would be compatible and would form a systematic unity.

The object in the idea must necessarily be supposed in order to comply with the demand of complete systematic unity, a demand belonging to the essence of reason, since it is precisely the supreme ground of systematic unity. In turn, systematic unity is a necessary condition for a corpus of cognitions to be considered as a science: “systematic unity is what first raises ordinary knowledge to the rank of science, that is, makes a system out of a mere aggregate of knowledge.”^[74] Such systematic unity is only possible under the guide of an idea.^[75] Thus, ideas and the object in the idea are not just non-deceptive, but necessary for legitimate knowledge. Rightly understood, the supposition of the object in the idea is not the absolute supposition of an actual object. Reason might legitimately conceive of a supreme ground of the systematic unity, but this ground lies beyond the limits of possible knowledge. It is not known, but merely conceived of in compliance with the subjective conditions of reason itself.

Reason demands in its transcendental maxim the pursuit of totality and presupposes in its Principle the object in the idea in which that totality is thought of as if it were already reached; but reason does not pretend actually having a complete knowledge of the object in the idea. Such knowledge of every single determination (or of every single condition) can be pursued only through scientific research carried out by understanding upon the data supplied by sensibility, a task which is beyond the attributes and functions of reason.^[76] Totality of conditions is just a demand of reason in its transcendental function of systematizing knowledge. It is not a pretension of having already reached this completeness.

Hence, we may conclude that the real use of reason, although it produces ideas of the kind metaphysics deals with, it does not incur into an illegitimate claim of a priori knowledge of things in themselves nor of objects whatsoever.^[77] Reason, in its real use, produces, besides principles, just ideas and their corresponding content, namely, objects in the idea.

The presupposition of the object in the idea is not a cognitive judgment immediately directed to objects. It does not regard the objects in the idea as actual objects, and it does not pretend that the systematic unity of the manifold objects of nature be more than an expectation or a subjective rule.^[78] The Principle enunciated in KrV A307/B364, that says: “if the conditioned is given, the whole series of conditions, subordinated to one another – a series which is therefore itself unconditioned – is likewise given, that is, is contained in the object and its connection” is valid, not as a Principle regarding things, but just as a necessary presupposition, in order that reason can accomplish its task of ascending toward the unconditioned. Klimmek expresses this clearly, as he reformulates the Principle as follows: “If the conditioned is given, the totality of its conditions is given as an object in the idea.”^[79] In this wording, the Principle becomes acceptable for Critical Philosophy. This presupposition becomes a dialectic principle (i.e., a misleading principle), only if we take it as a positive assessment that pretends to be an analytic truth meaning that the whole (unconditioned) series of the conditions is given in an actually existing object that can be found in experience. Yet, the right supposition of the Principle means just that the unconditioned is presupposed, though just as something undetermined. We conceive it as an object (properly as an object in the idea), merely because we cannot conceive of it otherwise than by means of the categories.^[80] Hence, real use of reason is not necessarily deceitful. It does not lead to unduly affirming the existence of a metaphysical actual thing. The productive activity of reason (its usus realis) leads to conceiving of a complete determinate object, though it does not lead to affirming the existence of an object corresponding to that concept^[81] (let alone the knowledge of such object). Kant remarks that the complete logical determination provides no indication of the actual existence of an object.^[82]

15 Divergent interpretations of the object in the idea

Although Kant clearly states that the object in the idea is “only a schema for which no object, not even a hypothetical one, is directly given,”^[83] some interpreters of the Critique of pure reason take the expression “object in the idea” in a different sense,^[84] stressing its aspect of an object which reason refers to.^[85] By so doing, the object in the idea becomes an object of the idea. Thus, the object in the idea is seen as something which has an existence separate from the idea itself. This interpretation amounts, in the long run, to deny legitimacy to the real use of reason, insofar as real use would then produce a non-sensible object that could entertain the pretention of having objective validity. A closer consideration of the concept of object in the idea prevents this interpretation, which is based mainly upon the chapter of the Critique of Pure Reason about “The Transcendental Illusion” (KrV A293/B349-51) and also in other passages, for instance KrV A339/B397: Dialectical sophisms “are not fictitious and have not arisen fortuitously, but have sprung from the very nature of reason. They are sophistications not of men but of pure reason itself.”

Deceit grounded on an illusory appearance originates in the fact that the regulative use of ideas, through which the data and the laws of experience are conceived of as if they were derived from an object in the idea,^[86] turns to be understood as an assertion claiming that these data and laws are actually derived from that object, which in its turn, is conceived of as actually existing. Thus, an alteration takes place: what was a legitimate object in the idea (Gegenstand in der Idee) comes to be conceived of as an actual object. What is here altered is not the content of the concept but the manner in which it is considered: in the one case the content of the concept is thought of as an object in the idea, in the other case it is thought of as an actually existing metaphysical object. Reason does rightly conceive of the relations empirical data and objects bear to the object in the idea.

Since the relation the data afforded by understanding bear to the object in the idea is identical to the relation the said data would bear to a metaphysical actual object, we may assume that it is this very identity of relations that gives rise to the illusion that the said data are subsumed under the concept of an unconditioned actual object taken as the term of the relation.

The said illusion is inevitable, as are optical illusions mentioned by Kant as illustrations in this context. Nevertheless, merely undergoing an illusion differs from granting assent to it. The illusion compels us to taking the object in the idea, together with all its determinations, for an actual object. Instead, all we are allowed to do is to suppose something (an unknowable unconditioned ground) as being actual; yet, we may not determine it, not even with the help of the rational concept of the object in the idea.

Error does not lie in reason’s real use, nor in the illusory appearance generated by reason, but in the mistaken judgment coming afterward. Indeed, the mistake lies in letting illusory appearance lead us to misinterpreting the object in the idea as an actual object.

16 How real use of reason is valid in spite of its generating an inevitable illusion

The regulative use of ideas is possible thanks to previous generation of them. This generation takes place by means of the real use of reason.^[87] We have come to the conclusion that this use of reason, which generates ideas, should be distinguished from a deceptive use. This is confirmed in the text KrV A669/B697 that states:

The ideas of pure reason can never be dialectical in themselves; any deceptive illusion to which they give occasion must be due solely to their misemployment. For they arise from the very nature of our reason; and it is impossible that this highest tribunal of all the rights and claims of speculation should itself be the source of deceptions and illusions.

In conclusion, real use of reason (the production of ideas and principles) is not necessarily deceitful, nor should it be underestimated as if it were mere incitement to a pre-critical metaphysics. This real use is necessary for experience to be enlarged to the full extent of its possibility. This can be achieved only if scientific research is guided by ideas. For the one thing, without the ideas of reason, science would be just natural history, namely a collection of unconnected facts.^[88] Besides, the ideas generated by the real use of reason are also necessary for the development of a critical metaphysics whose function is to point out the existence of a field that is inaccessible to knowledge. In spite of the fact that real use of reason gives rise to an inevitable illusory appearance, we can – and should – distinguish the said use (which is not deceitful) from the occurrence of yielding to the illusory appearance and being led into deceit by it.

17 A non-regulative albeit legitimate function of the real use of reason. Critical metaphysics based on the relative supposition.

This supreme reason is supposed as an object in the idea which is external to the sensible world and serves as its fundament. It can be no otherwise thought than by means of the categories of understanding, whose validity reaches no further than the sensible world; we can’t help thinking of it as if it were an object. This should not lead us to deceit, provided that we bear in mind that we are not determining the object such as it is in itself, but instead as an object in the idea, and provided also that we bear in mind that in so doing we are not making use of the categories with the aim of knowing the assumed object. We are only determining it through analogy with the objects constituted by the categories. We determine it then only insofar as such determination may be justified as a condition of the possibility of the systematic unity of the cognitions about the sensible world.

The regulative function of the ideas is fulfilled when the aggregate of data and laws of experience gathered by the understanding through its scientific research of the sensible world are considered as if the very empirical objects to which these data and laws refer, were actually derived from a single supersensible object (which exists solely as an object thought in the idea). Such supposition of an object from which everything derives (and consequently, such supposition of a systematic order in empirical objects) is just a suppositio relativa ^[89] made not in accordance with what the supposed object actually is, but in accordance with the subjective needs of our reason.

On conceiving the object in the idea, we do but comply with the subjective need of reason which demands to think it as were it an actual object and moreover as an object with certain characteristics. Yet, all I am allowed to suppose if I restrain myself within the limits drawn by the critique, is not an object in the full sense of it, but a relation: “I think to myself merely the relation of a being, in itself completely unknown to me, to the greatest possible systematic unity of the universe, solely for the purpose of using it as a schema of the regulative principle of the greatest possible empirical employment of my reason.”^[90] Now it is worth noting that on aiming at a never reached and unattainable limit, the idea framed by reason prevents the work of progressive determination from being held as finished and completed. In this way, it precludes whatever stage of scientific progress (as well as of prosyllogistic progress) from usurping the place of the unconditioned.^[91] By means of ideas, reason sets limits to sensibility. Karin de Boer expresses this with regard to the idea of soul: “The concept of the soul functions as a boundary stone that keeps sensibility at bay.”^[92] Such restriction turns out to be a positive result of critical metaphysics. This positive function of the ideas means more than just providing mere void heuristic hypothesis (as Willaschek means)^[93] and more than just defining the “context within which the constitutive principles of the understanding … can first be meaningfully employed.”^[94]

18 Real use of reason involves the possibility of conceiving a critical metaphysics

By means of the relative supposition of the object in the idea, we bring into relation the empirical objects – or the empirical laws of nature – with a non-empirical unknowable ground of them.

This supposition does not increase our knowledge of the said non-empirical ground: it is by no means an incursion into the intelligible world. Yet, thanks to that supposition we are able to refer our mind to the intelligible world even if only in a negative manner: it shows that the unity of the empirical laws of nature established by science depends on a condition (it shows that the said unity is not itself unconditioned) and that such condition does not belong to the sensible world, and therefore, it falls beyond the scope of our faculty of knowledge.

Therefore, critical Dialectic is not just destruction of metaphysics, but rather its depuration and the amendment of its illusions, a depuration undertaken “in order to pass beyond nature.”^[95] By these means, critical philosophy succeeds in extending itself up to the boundaries of the field of the suprasensible, though without trespassing into that field.

We necessarily presuppose this unattainable absolute ground as were it actual though unknowable, that is, as something outside the scope of our knowledge. “I shall not only be entitled, but shall also be constrained, to realise this idea, that is, to posit for it a real object. But I may posit it only as a something which I do not at all know in itself.”^[96]

In such a place as the supersensible condition should occupy (a place which is unattainable for our knowledge), we set those products of our reason which are the objects in the idea.^[97] We, thereby, do not determine the absent (lacking in our sensible world, though needed) condition; we do not know it, but we do become aware of its absence: our knowledge of the sensible world meets the lack of an unconditioned sufficient ground (which we should know if we were to have an utterly accomplished knowledge). Moreover, we realize that the sensible world is founded on an absolute ground (i.e., we acknowledge that empirical objects bear a relation to an unknown and unknowable x). Preserving an empty, though necessarily presupposed field inaccessible to knowledge, is another function of critical metaphysics. Kant states it explicitly as he writes: “the limits which it is compelled to set to its speculative employment likewise limit the pseudo-rational pretensions of all its opponents”^[98] who might perhaps claim the right of asserting the utter inexistence of that unattainable field.

The knowledge we seem to have about the object in the idea is in fact none other than reason’s knowledge about itself. Namely, all we can know about this object which we place instead of the stated unknowable x, is reason’s own claim. In other words, we can just become aware of what reason is exists by its own nature’s requirement. The proper purpose of critical theoretical metaphysics is not knowing the supersensible object which actually serves as ground for the sensible world. Rather than that, this theoretical metaphysics consists in the knowledge of the relation the systematic unity of the sensible world bears to an intelligible unknown factor; that is the relation with “a something of which, as it is in itself, we have no concept whatsoever, but which we none-the-less represent to ourselves as standing to the sum of appearances in a relation analogous to that in which appearances stand to one another.”^[99] All we do have in critical theoretical metaphysics is “only the idea of something which is the ground of the highest and necessary unity of all empirical reality.”^[100] The same is stated in another passage: “I think to myself merely the relation of a being, in itself completely unknown to me, to the greatest possible systematic unity of the universe.”^[101]

Such as Kant has taught in Prolegomena, the relative supposition complies with the limits^[102] imposed to knowledge by the critique. The relative supposition enables one to devise a metaphysics that avails itself of symbols^[103] (objects in the idea), which can be further determined through the procedure of analogy. Accordingly, we may say that the real use of reason, insofar as it enables us to conceive the object in the idea, performs a legitimate function in critical philosophy, both in the theory of knowledge, as well as in metaphysics.

19 Further development of a critical metaphysics based on real use of reason

With the legitimacy of the ideas generated by the real use of reason being granted (albeit under the previously exposed restrictive conditions), a critical metaphysics can be developed. Thus, the necessary supposition of the object in the idea (suppositio relativa),^[104] along with determining this object through analogy are, at least since the Prolegomena,^[105] the grounds for a metaphysics that does not trespass the limits imposed by the critique. This metaphysics set forth in the “Canon of pure reason” is later on widely developed in the Progress of metaphysics. ^[106]

In this last text, Kant presents a practico-dogmatic metaphysics in which the unconditioned practical reality provides a ground for dealing with those metaphysical questions that pure theoretical reason “is not able to ignore but which, as transcending all its powers, it is also not able to answer.”^[107] The ideas framed by the theoretical reason in its real use provide the conceptual tools for developing such practico-dogmatic metaphysics. Thus, these products of pure reason prove their legitimacy once again. Karin de Boer affirms her positive appreciation of the products of reason’s real use especially in practico-dogmatic metaphysics as she writes: “Kant did not regard these concepts as useless: insofar as they allow scientists to represent the unconditioned of their discipline in a determinate manner, they indirectly contribute to the cognition of objects of experience. More importantly, he held that these very concepts can acquire objective reality, or content, insofar as they are put in the service of practical reason.”^[108]

Real use of reason, explained and developed as it is in the second part of the appendix of the transcendental Dialectic, enables the rising of science. It also makes possible a critical metaphysics, insofar as it leads us to conclude that there is an ultimate fundament of knowledge which we are not capable to grasp; this might be conceived of as a purely negative result. Yet, we may frame or envisage this unknowable fundament, though not as it is in itself, but rather in relation to our subjectivity. Once we have conceived of this supersensible fundament according to the needs and possibilities of human reason, we may frame it as a relative supposition. Thus, real use of reason enables a cautious metaphysics that no longer pretends to know supersensible things as they are in themselves. Instead, this critical metaphysics acknowledges its subjectivity: it admits to be conditioned by its human origin and by the limitations depending on it.^[109] If we add to it the non-theoretical, but moral certainty (as is done in the Canon of pure reason)^[110] we obtain a practico-dogmatic metaphysics^[111] which is free from the objections affecting its merely theoretical pretension of knowing the unconditioned, without being reduced to a purely practical metaphysics.^[112]

These are altogether legitimate critical results of the unavoidable, yet legitimate real use of reason.