But if only we could see the rest of reality, mind, body, God, freedom, human life, with the same rush of clarity and understanding! Well, one philosophical ideal is that we can. This is the ideal of rationalism: the power of pure unaided reason. For the rationalist can see from her armchair that things must be one way and cannot be other ways, like the angle in the semicircle. Knowledge achieved by this kind of rational insight is known as ‘a priori’: it can be seen to be true immediately, without any experience of the way of the world.
