Below is part of a video of the brilliant Feynman expressing his views on some of these topics. The relevant points start at 3:20.
Anyway, the book that started this wretched chain of thoughts is David Deutsch's 'The fabric of reality' and it is quite simply, a work of genius. The brilliant thing about this book is that it boldly argues and presents conjectures on such difficult topics and manages to provide convincing arguments for its case. Deutsch doesn't dabble in mollifying opposing viewpoints and thus presents a book which is as incisive in its insight as it is overarching in its reach. He lays the grave of such philosophical junk as solipsism, inductivism, positivism and doesn't shy away from pointing where some of the most brilliant minds (Weinberg, Wheeler, Hawking, Penrose etc.) went wrong. He manages to narrow down his discussion to four of our best theories: quantum theory, Karl Popper's theory of epistemology, Darwinian evolution as modified by Dawkins, and theory of computation (Turing principle), presents the underlying unities among all of them and clarifies as to how all these theories, together, provide us with the most comprehensible and integrated view of our world yet. In other worlds, our first 'Theory of everything'. Its an intense book and I've already started it again in order to make more sense than the 5% I have managed to make after the first read .