Reasons Why first argues that what philosophers are really after, or at least should be after, when they seek a theory of explanation, is a theory of answers to why-questions. It then advances a thesis about what form a theory of answers to why-questions should take: a theory of answers to why-questions should say what it takes for one fact to be a reason why another fact obtains. The book's main thesis, then, is a theory of reasons why. Every reason why some event happened is either a cause, or a ground, of that event. Challenging this thesis are many examples philosophers have thought they have found of "non-causal explanations." Reasons Why uses two ideas to show that these examples are not counterexamples to the theory it defends. First is the idea that not every part of a good response to a why-question is part of an answer to that why-question. Second is the idea that not every reason why something is a reason why an event happened is itself a reason why that event happened. In the book's final chapter its theory of reasons why is extended to cover teleological answers to why-questions, and answers to why-questions that give an agent's reason for acting.
