Philosophy Rationalism
Kurt Smith
  • LAST REVIEWED: 21 January 2016
  • LAST MODIFIED: 21 January 2016
  • DOI: 10.1093/obo/9780195396577-0299


“Rationalism” denotes a family of philosophical views that have emerged over the past two millennia. Many of the views have in common the idea that the possibility of knowledge is rooted in certain inherent features of the mind. These features fall into at least three distinct though related categories. The first includes any feature that serves as an organizing principle, specifically organizing sensations or sensory data (e.g., colors, sounds, tastes, and so on), the result of which is a unified sensory experience. Such features account for what might be cast as the template or structure of experience. This structure, the emergence of which is “triggered” by instances of sensory data, is nevertheless thought to be prior to all instances of sensory experience in that its origin is in the mind, existing independently of the origin of sensations (or occurring sensory data). It is by way of this structure that the mind makes objects intelligible, where intelligibility in this context serves as a necessary condition for the possibility of knowledge. Such a feature is a principle of intelligibility. The second category includes any inherent feature that serves as a link between thoughts, a link that specifically preserves truth, such that if one thought (or proposition) is true, another thought (or proposition), distinct from the first, is true (i.e., it cannot be false if the first is true). Logical entailment is an example of such a feature (but other examples would be what are today called “logical operators,” such as conjunction, disjunction, and so on). One discovers this sort of link to hold between the thought of body A’s being shaped, for example, and the thought of body A’s being extended (in length, breadth, and depth), by understanding that it would be impossible to conceive the former without also conceiving the latter. In terms of truth, and in light of the present example, the link is revealed when understanding that in every conceivable case in which “A is shaped” is true “A is extended” is true. Truth-preservation in this context serves as a necessary condition for the possibility of knowledge. Such a feature is a principle of truth-preservation. The third category of inherent feature includes any capacity or faculty possessed by the mind that allows it to “access” whatever is taken to be the knowable (or the intelligible). Such a feature is a principle of access. None of the aforementioned features taken in isolation is sufficient for a system to be classified as a form of rationalism. Many philosophical systems are considered by their advocates to be “rationalist” in form based solely on the claim that reason, as opposed to sensory experience, secures the possibility of knowledge (whether in part or in whole).

General Overviews

The following readings should be of help to those interested in familiarizing themselves with rationalism or with important features of what are referred to as “rationalist” philosophical systems. Russell 1990 offers a very early and clear discussion of the features of rationalist systems. Lacey 1995 provides an excellent overview. Markie 2013 specifically identifies three theses attributed to such systems. Cottingham 1988 and Huenemann 2008 each offers a clear introduction to rationalism, focusing on systems developed in the 17th century. Lennon and Dea 2014 offers an excellent discussion of continental rationalism, which is typically associated with systems of the 17th century. Nelson 2005 offers perhaps the largest collection of essays available dealing with philosophical themes associated with rationalism, ranging from Plato (429–327 BCE) and Maimonides (1135–1204) to Donald Davidson (1917–2003) and Noam Chomsky (1928–). Last, Russell 2014 offers an excellent and helpful philosophical treatment of a priori justification and knowledge.

  • Cottingham, John. The Rationalists. Oxford: Oxford University Press, 1988.

    This book deals specifically with the 17th-century philosophical systems of René Descartes (1596–1650), Baruch Spinoza (1632–1677), and Gottfried Leibniz (1646–1716). The book is perfect for the undergraduate. In addition to providing an excellent background, both historical and philosophical, Cottingham provides concise accounts of how these rationalist systems handled philosophical topics such as method, substance, mind, matter, freedom, and morality.

  • Huenemann, Charlie. Understanding Rationalism. Stocksfield, UK: Acumen, 2008.

    This book is perfect for the undergraduate. Along the lines of Cottingham 1988, Huenemann’s book deals with specific features of the 17th-century systems of Descartes, Spinoza, and Leibniz. That said, it is not an overview of these systems. In particular, the book focuses on Descartes’s dualism and his moral psychology as developed in the Passions; on Spinoza’s substance monism and his political and religious views; and on Leibniz’s monadic metaphysics and his views on justice and freedom.

  • Lacey, Alan. “Rationalism.” In The Oxford Companion to Philosophy. Edited by Ted Honderich, 741–744. Oxford: Oxford University Press, 1995.

    This is a short, informative, and detailed article that covers rationalisms (plural), tracing the movement from antiquity to the 20th century.

  • Lennon, Thomas M., and Shannon Dea. “Continental Rationalism.” In Stanford Encyclopedia of Philosophy. Edited by Edward N. Zalta. (Spring 2014 Edition). Stanford, CA: Stanford University.

    This is an online encyclopedia article. In addition to Descartes, Spinoza, and Leibniz, the view of Nicolas Malebranche (1638–1715) is discussed.

  • Markie, Peter. “Rationalism vs. Empiricism.” In Stanford Encyclopedia of Philosophy. Edited by Edward N. Zalta. (2013 Edition). Stanford, CA: Stanford University.

    This is an online encyclopedia article. Markie identifies three theses typically attributed to rationalist philosophical systems: the intuition/deduction thesis, the innate knowledge thesis, and the innate concept thesis. As the title suggests, the article sets out to draw a variety of distinctions between rationalism and empiricism. This introduces readers to several of the classical arguments made for and against rationalism.

  • Nelson, Alan, ed. A Companion to Rationalism. Oxford: Blackwell, 2005.

    This volume is a collection of twenty-five first-rate essays dealing with a variety of philosophical themes associated with rationalism. Although the volume focuses most heavily on the rationalist systems of the 17th and 18th centuries, some essays have much to say about ancient and medieval views, and others have much to say about views advanced as late as the 20th century.

  • Russell, Bertrand. The Problems of Philosophy. Indianapolis, IN: Hackett, 1990.

    Although it considers several problems associated with philosophical inquiry, generally understood, the book offers clear and helpful analyses of the role of reason, the possibility of a priori knowledge, and the general underpinnings of a rationalist philosophical system. This is considered now to be a classic, originally published in 1912.

  • Russell, Bruce. “A Priori Justification and Knowledge.” In Stanford Encyclopedia of Philosophy. Edited by Edward N. Zalta. (Summer 2014 Edition). Stanford, CA: Stanford University.

    In this online entry the reader will find an excellent philosophical discussion of the concepts of a priori justification and knowledge. The entry’s bibliography is an excellent resource of the most recent important work in this area.

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