4. Transcendental arguments involve transcendental claims, to the effect that X is a necessary condition for the possibility of Y, where in saying this, the arguments do not assume this to be a matter of merely causal or natural necessity. Given that their target is the skeptic who challenges our claims about the world, there are clearly two good reasons for this. First, although our observation of the world might suggest that experience has certain necessary causal conditions (e.g., light and s