Rationalism
Authors: Markie Peter J. 
Published: September 2018

Rationalism is the view that reason, as opposed to, say, sense experience, divine revelation or reliance on institutional authority, plays a dominant role in our attempt to gain knowledge. Different forms of rationalism are distinguished by different conceptions of reason and its role as a source of knowledge, by different descriptions of the alternatives to which reason is opposed, by different accounts of the nature of knowledge, and by different choices of the subject matter, for example, ethics, physics, mathematics, metaphysics, relative to which reason is viewed as the major source of knowledge. The common application of the term ‘rationalist’ can say very little about what two philosophers have in common.
Suppose we mean by reason our intellectual abilities in general, including sense experience. To employ reason is to use our individual intellectual abilities to seek evidence for and against potential beliefs. To fail to employ reason is to form beliefs on the basis of such non-rational processes as blind faith, guessing or unthinking obedience to institutional authority. Suppose too that we conceive of knowledge as true, warranted belief, where warrant requires that a belief be beyond a reasonable doubt though not beyond the slightest doubt. Here, then, is a version of rationalism: reason is the major source of knowledge in the rational sciences. This is a weak version of rationalism which simply asserts that our individual intellectual abilities, as opposed to blind faith and so on, are the major source of knowledge in the natural sciences. It is clearly not very controversial and is widely accepted.
Suppose, however, we take reason to be a distinct faculty of knowledge distinguished from sense experience in particular. To employ reason is to grasp self-evident truths or to deduce additional conclusions from them. Suppose we conceive of knowledge as true, warranted belief, where warrant now requires that a belief be beyond even the slightest doubt. Let us also extend our attention to metaphysics and issues such as the existence of God, human free will and immortality. Here is a much stronger version of rationalism which asserts that the intellectual grasp of self-evident truths and the deduction of ones that are not self-evident is the major source of true beliefs warranted beyond even the slightest doubt in the natural sciences and metaphysics. Clearly it is highly controversial and not very widely accepted.
The term ‘rationalism’ has been used to cover a range of views. Scholars of the Enlightenment generally have in mind something like the first example – a general confidence in the powers of the human intellect, in opposition to faith and blind acceptance of institutional authority, as a source of knowledge – when they refer to the rationalist spirit of the period and the work of such philosophers as Voltaire. Most frequently, the term ‘rationalism’ is used to refer to views, like the second one above, which introduce reason as a distinct faculty of knowledge in contrast to sense experience. Rationalism is then opposed to empiricism, the view that sense experience provides the primary basis for knowledge. This entry concentrates on this still very general form of rationalism, reserving the term ‘rationalism’ for it alone.