A conundrum: my favorite philosophers – Aristotle, Thomas and Plato – don’t spend much ink on trying to answer the questions raised by radical doubt, although they were clearly aware of them. Instead, they just stick to the obvious: that, IF you are standing here having this discussion/reading this book, THEN you’ve already answered your radical doubt questions in a certain way – and let’s look at what we can figure out from your answer.
This is certainly wise, and in fact an approach I have used myself (eschewing, with reluctance, the equally valid approach of sneaking up behind people who claim to be uncertain about everything and whacking them in the back of the head, and then assuming a posture of total innocence when they turn around – you know, inviting them to consider deeply their new-found certainty about the external world). But I, being neither as smart nor wise, cannot seem to stay away from it – every time I hear somebody claim to rely on pure, unadulterated Reason, I start to gag and want to drag them down the path to radical doubt, just to show them how STUPID claims of radical reasonableness are. Choosing to use reason as your evaluation tool is delusional on two fronts: There’s no purely reasonable basis upon which to choose reason over unreason, and what people typically call ‘reasonable’ is polluted through and through with unspoken, unacknowledged whims – assumptions and assertions that are not remotely reasonable except in a completely circular way: what I choose is reasonable because I only choose reasonable things.
Oops, there I go again.
The challenge, it seems, is to embrace the wisdom of my Big Three and avoid the folly of vastly lesser minds (Descartes, I’m talkin’ to you!) and proceed, as Aristotle advises, from what is most easily known to us to what is most perfectly known in itself.
Yard Sale of the Mind 