Definition of Philosophy

They [Philosophers] are striving towards a fundamental understanding of whatever exists, including ourselves. And they are trying to do this without making it a question of religious faith, or appealing to the say-so of an authority. They may as individuals have religious beliefs - most great philosophers have had, though some have not - yet as good philosophers they do not attempt to support their philosophical arguments with appeals to religion. A philosophical argument is one that carries its own credentials with it, in the form of reasons: it asks you for your rational assent, not for faith or obedience. Philosophy tries to see how far reason alone will take us.

Because philosophy is a quest for rational understanding of the most fundamental kind it raises important questions about the nature of understanding and hence of enquiry and knowledge. How are we to go about finding answers to all these questions of ours? Can we ever really know, in the sense of being sure of, anything? If so, what? And even if we do know, how will we be able to be sure that we know; in other words can we ever know that we know? Questions like this have themselves come to occupy a place near the centre of philosophy. Alongside questions about the world around us, the philosopher asks questions about the nature of human perception, experience, and understanding.

So, put at its most basic, philosophy has developed in such a way that two fundamental questions lie at its heart: the first is "What is the nature of whatever it is that exists?" and the second is "How, if at all, can we know?" Investigation into the first question, about what exists and the nature of existence, constitutes the branch of philosophy known as ontology. Investigation into the second question - about the nature of knowledge, and what, if anything, we can know - is called epistemology. It is the development of these two over the centuries - and of all the subsidiary questions that arise out of them - that constitute the mainstream of philosophy's history.

The Story of Philosophy. Magee, Bryan. (Dorling Kindersley 1998). PP 7 - 8.