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Not to be confused with Rationality, which simply refers to the process of being reasonable.

Rationalism is a philosophy in which a high regard is given to reason (specifically logic) and to empirical observation.[1]

From the strict philosophical standpoint, rationalism is the view that all or most truth is deductive and a priori, deriving logically from a set of axioms gained by intuition or inherent knowledge (and not from studying the world around us empirically).[2] However, the term is not very often used so strictly, so this form of rationalism is generally known in English-speaking philosophy as continental rationalism or Cartesian rationalism, as its original proponents, such as René Descartes, largely did their philosophising in continental Europe.[3]

The term is more commonly used to refer to a synthesis of continental rationalism with its former rival philosophy, empiricism. This looser rationalism holds that empirical observation is more useful than intuition for gaining one's starting axioms, but one can use deductive reasoning from these axioms just as well. The best embodiment of this way of gaining knowledge is the scientific method; hence, rationalists tend to give high regard to science, designating it as the primary or sole proper source of truth.

RationalWiki is devoted to this sort of rational analysis of empirical evidence to form conclusions; most RationalWiki editors are very skeptical of other ways of knowing.


General use[edit]

See the main article on this topic: Rationality

The idea of being "rational" is distinct and broader than the philosophy of rationalism. To be "rational" is synonymous with a "sane" or "functional" way of thinking. If one is "rational," then in common parlance this means that one can think clearly and is capable of intelligently assessing new ideas when presented.

The opposite term, "irrational," is used to signify someone who cannot or will not think clearly. If a thought or action is “irrational,” it signifies something that is not just incorrect, but perverse, insane, or beneath consideration.

Historical rationalism[edit]

Rationalism was first formulated in classical times by philosophers such as Socrates and Plato. Many of the Socratic dialogues would use a conversational process to work out logical inconsistencies in ideas that were held by contemporaries to be "common sense," such as the definition of "the good." In this historical sense Rationalism was distinct and separate from Empiricism (see below), as these early Rationalists didn't deem it necessary to use observation - in the modern use, Rationalists who would combine both the logical reasoning of Rationalism with the observational checks of Empiricism.

But at the time, virtually everyone — even the great philosophers — believed that various things were known by people inherently. Aside from a few schools of thought which suggested that nothing could ever be known as true (pyrrhonism), few thought to discard a priori beliefs and start from scratch with only that which was known to be true. Thus, at this point historical Rationalism closely resembled the way philosophers still define the philosophy.

The 16th century philosopher Descartes, however, attempted to create a whole philosophy through pure reason in his Discourse on Method and its succeeding works: he began with the only thing of which he thought he could be certain, that there was an "I" that was thinking - often rendered in the Latin of cogito ergo sum ("I think, therefore I am."). His process ushered in a new era in rationalism, concurrent with the greater Enlightenment. At that time the philosophy began to resemble modern empiricism more than its own ancient ancestor, especially during the era of Romanticism when Enlightenment ideas were challenged and sensory perception was given more of a hearing.

Loose use in the time since has led to the fuzzy state of the term today, particularly when combined with the similar but much broader notion of being rational.

Rationalism in psychology[edit]

Rationalism in psychology is identified with the philosophical tradition of the same name and refers to the school of thought that sees certain elements of cognition as innate. For this reason, it is sometimes used synonymously with the terms "innatism" or "nativism" though the synonymy is not particularly deep as "innatism" or "nativism" sees them as innate in the thicker sense of that one at least can be born with them preset exactly in a certain, perhaps permanent, way (whether this ever actually happens is beside the point) and Rationalism sees them as innate in the thinner sense that one is simply born with them waiting to be set more exactly as one is psychologically prepares to understand what they are about and perhaps never completely fixable once set for the first time. During the 20th century, Noam Chomsky became associated with rationalism due to his positing the concept of an innate "language acquisition device."[4]

Rationalism in economics[edit]

Rationalism, or "economic rationalism," is also a term of art in economics. It is generally used today in Australia to refer to the local brand of neoliberal economic and political policy, though it was also used by scholars such as Max Weber in reference to the Protestant work ethic.[5]

Other contemporary uses[edit]

Rationalism is also used as a self-descriptor by followers of Eliezer Yudkowsky, and the community that has grown up around him (in particular the website LessWrong).[6] Scott Alexander argues that, in this context, it refers less to a particular set of beliefs (an ideology), but more to the social community those beliefs support, a "tribe".[6]

Means-ends rationalism[edit]

Another straightforward conception of rationality is that an individual acts rationally if they act in the way that, on reflection, they believe best suits achievement of their aims. This conception, naturally, gives rise to the common conception when “on reflection” it is believed that the aim of truth can best be achieved through factual analysis and the scientific method.

This approach, however, is problematic, as it denies the existence of any sort of objective logic independent of human perception. Many, on reflection, believe that astrology, Scientology, homeopathy and other ridiculous nonsense best suits achievement of their aims. If these people are to be held to be irrational, a new criterion must be put in the place of “on reflection”. Usually the criterion is modified such that the rational person must “reasonably believe” they have a methodology to achieve their aims, leaving question of what it means to “reasonably believe” that a methodology will achieve certain aims.[7]

Sanity and proper function[edit]

Alvin Plantinga's concept of rationalism neatly distinguishes reason from "raving madness" by conceiving of reason as "not raving mad".[8] Of course Plantinga has to give us a good idea of what is not "raving mad", which he does with his concept of "proper function". Just as a clock, functioning properly, is a reliable indicator of the time, human senses, functioning properly, are reliable indicators of the world. Acting in accordance with the proper function of our faculties is rational.

The problem of what constitutes function, and proper function at that, is more than a question of what our faculties do (a fast clock tells the incorrect time, but this is not its function). Both function and proper function have an element of what things should be doing. As should is a difficult concept to introduce in a mechanistic description of how things happen to be, Plantinga sources the "should", the "purpose" of our faculties in a concept of God.

Critical rationalism[edit]

Critical rationalismWikipediaKarl Popper) differentiates from the above conceptions of rationality by rejecting any positive content in reason. “Reason”, critical rationalism holds, does not provide 'reasons': it does not give positive recommendations about what beliefs should be held. Reason operates negatively, restricting the beliefs that can be held. It does this through criticism, subjecting pre-adopted beliefs to tests in an effort to refute them.

Empiricism versus Rationalism[edit]

The dispute between rationalism and empiricism concerns the extent to which we are dependent upon sense experience in our effort to gain knowledge. Rationalists claim that there are significant ways in which our concepts and knowledge are gained independently of sense experience. Empiricists claim that sense experience is the ultimate source of all our concepts and knowledge.

Rationalists generally develop their view in two ways. First, they argue that there are cases where the content of our concepts or knowledge outstrips the information that sense experience can provide. Second, they construct accounts of how reason in some form or other provides that additional information about the world. Empiricists present complementary lines of thought. First, they develop accounts of how experience provides the information that rationalists cite, insofar as we have it in the first place. (Empiricists will at times opt for skepticism as an alternative to rationalism: if experience cannot provide the concepts or knowledge the rationalists cite, then we don't have them.) Second, empiricists attack the rationalists' accounts of how reason is a source of concepts or knowledge.

A serious problem for the Innate Knowledge thesis remains, however. We know a proposition only if it is true, we believe it and our belief is warranted. Rationalists who assert the existence of innate knowledge are not just claiming that, as a matter of human evolution, God's design or some other factor, at a particular point in our development, certain sorts of experiences trigger our belief in particular propositions in a way that does not involve our learning them from the experiences. Their claim is even bolder: In at least some of these cases, our empirically triggered, but not empirically warranted, belief is nonetheless warranted and so known. How can these beliefs be warranted if they do not gain their warrant from the experiences that cause us to have them or from intuition and deduction?

Some rationalists think that a reliabilist account of warrant provides the answer. According to Reliabilism, beliefs are warranted if they are formed by a process that generally produces true beliefs rather than false ones. The true beliefs that constitute our innate knowledge are warranted, then, because they are formed as the result of a reliable belief-forming process. Carruthers maintains that “Innate beliefs will count as known provided that the process through which they come to be innate is a reliable one (provided, that is, that the process tends to generate beliefs that are true)” (1992, p. 77). He argues that natural selection results in the formation of some beliefs and is a truth-reliable process.

An appeal to Reliabilism, or a similar causal theory of warrant, may well be the best way for rationalists to develop the Innate Knowledge thesis. They have a difficult row to hoe, however. First, such accounts of warrant are themselves quite controversial. Second, rationalists must give an account of innate knowledge that maintains and explains the distinction between innate knowledge and a posteriori knowledge, and it is not clear that they will be able to do so within such an account of warrant. Suppose for the sake of argument that we have innate knowledge of some proposition, P. What makes our knowledge that P innate? To sharpen the question, what difference between our knowledge that P and a clear case of a posteriori knowledge, say our knowledge that something is red based on our current visual experience of a red table, makes the former innate and the latter not innate? In each case, we have a true, warranted belief. In each case, presumably, our belief gains its warrant from the fact that it meets a particular causal condition, e.g., it is produced by a reliable process. In each case, the causal process is one in which an experience causes us to believe the proposition at hand (that P; that something is red), for, as defenders of innate knowledge admit, our belief that P is “triggered” by an experience, as is our belief that something is red. The insight behind the Innate Knowledge thesis seems to be that the difference between our innate and a posteriori knowledge lies in the relation between our experience and our belief in each case. The experience that causes our belief that P does not “contain” the information that P, while our visual experience of a red table does “contain” the information that something is red. Yet, exactly what is the nature of this containment relation between our experiences, on the one hand, and what we believe, on the other, that is missing in the one case but present in the other? The nature of the experience-belief relation seems quite similar in each. The causal relation between the experience that triggers our belief that P and our belief that P is contingent, as is the fact that the belief-forming process is reliable. The same is true of our experience of a red table and our belief that something is red. The causal relation between the experience and our belief is again contingent. We might have been so constructed that the experience we describe as “being appeared to redly” caused us to believe, not that something is red, but that something is hot. The process that takes us from the experience to our belief is also only contingently reliable. Moreover, if our experience of a red table “contains” the information that something is red, then that fact, not the existence of a reliable belief-forming process between the two, should be the reason why the experience warrants our belief. By appealing to Reliablism, or some other causal theory of warrant, rationalists may obtain a way to explain how innate knowledge can be warranted. They still need to show how their explanation supports an account of the difference between innate knowledge and a posteriori knowledge.

See also[edit]


  1. Rationalism, Encyclopaedia Britanica
  2. Rationalism vs. Empiricism, Standard Encyclopaedia of Philosophy
  3. Continental Rationalism, Stanford Encyclopedia of Philosophy.
  4. Innatist/Innate/Nativist/Rationalist/Mentalist Theory
  5. John Quiggin. Economic Rationalism. Crossings, 2(1), 3-12.
  6. 6.0 6.1 Scott Alexander, The Ideology Is Not The Movement, Slate Star Codex
  7. Badly summarised from Alvin Plantinga, A. Warrant: The Current Debate. Oxford University Press. Oxford. 1993. p132.
  8. Badly summarised from Plantinga, A. Warrant: The Current Debate. Oxford University Press. Oxford. 1993. p134.