Foundationalism is a sound theory of epistemic justification

A. Locke's Veil of PerceptionMy opponent brings up John Locke's idea that the empirically minded senses which we rely on to sense the world are unreliable and hence a sound theory of absolute epistemic justification (at least in the foundationalist list sense) is not possible. My opponent's point however fails to realize that even if empirical observations are not sufficient to yield justified belief, this does not prove that either (A) no justified belief is possible or (B) that foundationalism fails to justify the type of knowledge possible. Lock's 'Veil of Perception' argument understandably calls into question whether or not one's sensual faculties are able to sufficiently justify belief or relate true pictures of the outside world to the sensor. After all, my feeling of a stove being hot doesn't necessarily prove that it actually is, only that I am at that point feeling heat. It's within the realm of possibility that some evil Demon is simply playing a trick on my senses[1] or that my brain has been secretly transferred into a vat[2]. However, this does not mean justified belief is an impossible ideal. Consider Descartes famous dictum, "Cogito ergo sum" (I think therefore I am). Surely one is justified in believing that one's self exists out of necessity (meaning we know this non-inferentially) since the very action of calling one's existence into questions implies existence. Hence denial of one's existence results in performance contradiction[3].On whether or not foundationaslist best comrd to explain how we come to justify this belief, one must simply look to the concepts inherent in foundationalism. Foundationalism is based off of the idea that all justified belief necessarily comes back to a single (or set of) non-inferentially justified beliefs. Cog It ergo sum fulfills the criterion for this exactly seeing as it is non-inferentially justified and seems the best building block upon which other pieces of knowledge may be added. After all, one can't prove that other entities exist, reflect on their characteristics or relations to others, etc. unless one may actually be justified in believing in an observer to observe these facts in the first place.B. Hume's SkepticismOn causation and Mr. Hume's characteristic skepticism of such a thing being proved to exist, I will respond with Kant and his principle of causality. Kant begins with the observation that we are in a state of "temporal irreversibility", meaning that time goes "forward" and not backward. The sequence of events has a certain temporal order. From this Kant reasoned, the only way in which we are able to make sense of the "direction" in which time and the sequence of events move is by recognizing cause and effect (later events being caused by earlier events) is a necessary conclusion.[4]On the point of non-inferential epistemic justification, my opponent suggests that it cannot be a method to justified true belief because even "the most intrinsically true" propositions i.e. non-inferential propositions are mere extensions of perception. From what I can understand, what my opponent is saying is that since all knowledge comes from perception, all knowledge is necessarily inferred, meaning non-inferential knowledge is impossible, destroying the crux of the entire foundationalist argument. I would ask my opponent why non-inferential knowledge must necessarily be an extension of perception. The reason I know that adding two to itself produces the sum of four is not because I have inferred this from countless observations of this occurring in the outside world, but because it's definition entails the sum. Therefore it must be admitted that at the very least some knowledge doesn't need to go through a sensory channel as in the case of mathematics and logic.===Sources===[1] http://www.groupsrv.com...[2] http://www.iep.utm.edu...[3] http://en.wikipedia.org...[4] http://plato.stanford.edu...