At its simplest, philosophy (from the Greek phílosophía or phílosophía, meaning ‘the love of wisdom’) is the study of knowledge, or "thinking about thinking", although the breadth of what it covers is perhaps best illustrated by a selection of other alternative definitions:
the discipline concerned with questions of how one should live (ethics); what sorts of things exist and what are their essential natures (metaphysics); what counts as genuine knowledge (epistemology); and what are the correct principles of reasoning (logic) (Wikipedia)
investigation of the nature, causes, or principles of reality, knowledge, or values, based on logical reasoning rather than empirical methods (American Heritage Dictionary)
the study of the ultimate nature of existence, reality, knowledge and goodness, as discoverable by human reasoning (Penguin English Dictionary)
the rational investigation of questions about existence and knowledge and ethics (WordNet)
the search for knowledge and truth, especially about the nature of man and his behavior and beliefs (Kernerman English Multilingual Dictionary)
the rational and critical inquiry into basic principles (Microsoft Encarta Encyclopedia)
the study of the most general and abstract features of the world and categories with which we think: mind, matter, reason, proof, truth, etc. (Oxford Dictionary of Philosophy)
careful thought about the fundamental nature of the world, the grounds for human knowledge, and the evaluation of human conduct (The Philosophy Pages)
As used originally by the ancient Greeks, the term "philosophy" meant the pursuit of knowledge for its own sake, and comprised ALL areas of speculative thought, including the arts, sciences and religion.
Philosophical questions (unlike those of the sciences) are usually foundational and abstract in nature. Philosophy is done primarily through reflection and does not tend to rely on experiment, although the methods used to study it may be analogous to those used in the study of the natural sciences.
In common usage, it sometimes carries the sense of unproductive or frivolous musings, but over the centuries it has produced some of the most important original thought, and its contribution to politics, sociology, mathematics, science and literature has been inestimable. Although the study of philosophy may not yield "the meaning of life, the universe and everything", many philosophers believe that it is important that each of us examines such questions and even that an unexamined life is not worth living. It also provides a good way of learning to think more clearly about a wide range of issues, and its methods of analyzing arguments can be useful in a variety of situations in other areas of life.
Philosophy is such a huge subject that it is difficult to know how to break it down into manageable and logical sections. Perhaps the most basic overall split at the highest level is geographical, between Eastern Philosophy and Western Philosophy (with, arguably, African Philosophy as a possible third branch at this level).
