unprovable assumptions, like the utiliity of induction
One might call induction an "undeniable assumption" instead: we cannot do without it; it's part of what we are. As a matter of human nature (and, indeed, the nature of all other animals (and computer programs) capable of learning), we do use induction, regardless of whether we can prove it. Some of the best evidence for induction might be rather crudely anthropic: we, who implicitly and constantly use induction, are here; creatures with anti-inductive priors are not here.
Do you believe in an objective morality capable of being scientifically investigated (a la Sam Harris *or others*), or are you a moral nihilist/relativist? There seems to be some division on this point. I would have thought Less Wrong to be well in the former camp.
Edit: There seems to be some confusion - when I say "an objective morality capable of being scientifically investigated (a la Sam Harris *or others*)" - I do NOT mean something like a "one true, universal, metaphysical morality for all mind-designs" like the Socratic/Platonic Form of Good or any such nonsense. I just mean something in reality that's mind-independent - in the sense that it is hard-wired, e.g. by evolution, and thus independent/prior to any later knowledge or cognitive content - and thus can be investigated scientifically. It is a definite "is" from which we can make true "ought" statements relative to that "is". See drethelin's comment and my analysis of Clippy.