PHL112: Survey of Modern Philosophy

THESIS: "I must once and for all seriously undertake to rid myself of all the opinions which I had formerly accepted, and commence to build anew from the foundation . . . to establish any firm and permanent structure in the sciences." (Descartes, Meditations, p.5)

PRO: In keeping my checkbook, if the entries are unreliable, no matter how carefully I calculate, the result of my calculation will not accurately reflect my balance. Similarly, in the sciences, if the evidence from which we start is unreliable, no matter how well and validly we reason from these assumptions, so will our conclusions be unreliable. And if the assumptions are false, the conclusions I reach -- no matter how carefully reasoned -- will likewise, almost certainly, be false. And no doubt, many things we do believe we believe for insufficient reasons, and some of these things, consequently, almost certainly are false. So we should try, insofar as possible, to base our scientific reasoning on evidence which is certain so that our conclusions might be well-founded.

CON: The house of belief is one we have to inhabit. We can't just move out and start building anew; we have to live there all the while we're making renovations. You might -- switching metaphors -- compare the whole body of our beliefs to a ship at sea. We can undertake repairs to one part or another of the ship while remaining afloat; but we can't undertake to rebuild the whole ship all at once without sinking. You might compare such radical doubt as Descartes attempts -- trying to doubt even the evidence of the senses, the existence of the external world, and the truths of math -- to such a misguided attempt at ship repair.

CONCLUSION: Perhaps -- pursuing the ship analogy -- the scientist's laboratory and the philosopher's study are like dry dock. There where one is "not considering the questions of action, but only of knowledge" (p.7) it may, after all, be possible to "pretend that all these opinions [that are in the least doubtful] are entirely false and imaginary" and there will be "neither peril nor error in this course" (p.7).