Thoughts, Words, and Promises: Fides and the Legal Significance of the Inner Sphere
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Talya Deibel
Talya Deibel is an assistant professor of Health Law and Ethics at Maastricht University, the Netherlands. Before joining Maastricht University, she worked as a senior postdoctoral researcher in the
Law and the Inner Self Project, funded by a Research Ireland Laureate (Consolidator) grant (2022/2628) at University College Cork, Ireland. She earned her LLM in Law and Economics (2012) and her PhD in Private Law (2012) from Bilkent University. After completing her PhD, she held various visiting postdoctoral positions across Europe, including at the Oxford Institute of European and Comparative Law, the UNIDROIT Institute, and the Amsterdam Centre for Transformative Private Law. Talya’s interdisciplinary research revitalizes the fundamentals of European private law and legal philosophy, particularly in the context of ethics of emerging technologies.
Abstract
This paper traces how the Roman notion of fides evolved into the concept of good faith, which is central to contract law theory. It explores how fides was initially understood in Roman society as a divine presence within the inner sphere of individuals, symbolizing honesty and loyalty in social relationships. To illustrate how fides transitioned into the legal domain through natural law and procedural law, the paper examines three key developments over the longue durée of European private law: the emergence of the bonus vir (good and reasonable man) standard, the evolution of consensual contracts, and the doctrine of aequitas naturalis (natural equity). The legal evolution of good faith from a moral-religious phenomenon to a legal principle highlights how loyalty to promises and honesty, which belong to the inner sphere, and their relationship to their outward manifestations were addressed in law. It also demonstrates how the values tied to fides became integral to European legal traditions thereby shaping modern contract law.
Funding source: Research Ireland
Award Identifier / Grant number: 2022/2628
About the author
Talya Deibel is an assistant professor of Health Law and Ethics at Maastricht University, the Netherlands. Before joining Maastricht University, she worked as a senior postdoctoral researcher in the Law and the Inner Self Project, funded by a Research Ireland Laureate (Consolidator) grant (2022/2628) at University College Cork, Ireland. She earned her LLM in Law and Economics (2012) and her PhD in Private Law (2012) from Bilkent University. After completing her PhD, she held various visiting postdoctoral positions across Europe, including at the Oxford Institute of European and Comparative Law, the UNIDROIT Institute, and the Amsterdam Centre for Transformative Private Law. Talya’s interdisciplinary research revitalizes the fundamentals of European private law and legal philosophy, particularly in the context of ethics of emerging technologies.
Acknowledgments
The author would like to thank Professor Patrick O’Callaghan for his comments and suggestions on earlier drafts.
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Research funding: This work was supported by the Research Ireland (2022/2628).
© 2025 Walter de Gruyter GmbH, Berlin/Boston
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Articles in the same Issue
- Frontmatter
- Editorial
- Constitutional Theory as Literature in the 19th-Century Anglosphere
- Focus
- Charles Dickens, Albert Venn Dicey, and Openness in the Anglosphere
- Rhetoric and Empire: Constitutional Thought and Literature in the 19th-Century Anglosphere
- Authoring the Nation: Madame de Staël and the Literary Origins of the State
- The End of the Victorian Era: Reflections on an Edwardian Viewpoint
- Illustrating the Indian Penal Code: Bigamy, the Victorian Novel, and the Formation of National Identity
- The Christian Year – Still Needed? John Keble on the ‘Co-Extensiveness’ of Church and State
- Research
- We Have Never Been Persons!
- A Tragic Photograph: Emotional Journey of a Political Spectator
- Thoughts, Words, and Promises: Fides and the Legal Significance of the Inner Sphere
