Kantian Reason

Three familiar uses of the term 'reason' are to signify a cause, a purpose, or a justification. An example of a cause is, 'The reason the grass is wet is that it rained last night'. An example of a purpose is, 'The reason that I am out walking is that I am going to the library'. An example of a justification is 'The reason that I believe that he is lying is his shifty eyes'. So, in common parlance, last night's rain, my wanting to go to the library, and a man's countenance are the 'reasons' in their respective cases. However, each example suppresses a general proposition--in the first, 'Rain wets objects'; in the second, 'Walking is a means of transportation'; in the third, 'Shifty eyes is a sign of a liar'. More accurately, it is these general propositions that are the 'reasons' in each case, i. e. by them alone can otherwise mere facts become cause, purpose, or justification. Similarly, why Kant does not settle on defining Reason as 'the power of inference' is that it is, more fundamentally, the source of Principles, i. e. the major premises from which deductive inferences are drawn, and of Ideas, i. e. the notions of totalities entailed by Principles. Hence, for example, Pure Practical Reason's 'Act only on that maxim that you can at the same time will to be a universal law' provides a Principle from which specific correct conduct can be deduced, and entails the Idea of a totality of rational agents, i. e. his 'kingdom of ends'. Thus, this fundamental character of Reason serves as an unstated ground of Kant's challenge to Humean Moral Sentimentalism. For, the latter holds that Universal Sympathy is the basis of Morality, and, hence, that Morality is essentially irrational. But, the Kantian response is that Reason is the sole source of any notion of Universality, so even Sentimentalism is Rational, at heart.