Of the great aims of liberal education critical reasoning (the combination of the attitude and the capacity to ask the right questions and to think things through) has always been the most pursued and the hardest to impart. It is pursued because it is a presupposition of the others or of the correct exercise of the others. It is hard because it involves an art, a science, and a way of life. A way of life is lived and an art is learned by doing. Still what this book aims to do is to ground critical thinking on that part of the science of logic that is secure, propositional and predicate calculus, and to proceed from there to further applications of logical theory in the general methodology of thought. The last part applies these lessons in critical thinking to a consideration of two problems in philosophy, the problem of god and the problem of mind.