Philosophy, which to the ancient Greeks meant 'love of wisdom', is about man's search for an understanding of his world, and of himself. Ranging over every branch of human thought, it asks how life should be lived, and what knowledge is and how it is acquired.
It devises systems of ideas to explain human thought and knowledge; and it deduces conclusions from propositions by means of reasoned argument.
In the modern world, two main schools of thought compete. One system teaches that nothing can be taken at face value, and that everything must be proved by observation and experiment. The rival school sees philosophy as a tool for changing society, by equipping men with a complete system embracing every possible human experience.