What is philosophy?
Philosophy is the study of the fundamental nature of existence. It is the base on which all the special sciences (such as physics, biology, and economics) depend. Philosophy, therefore, is itself a science. It is not an arbiter between fact and faith, as it is widely presented today.
The five branches of philosophy
Metaphysics is the study of the nature of the universe as a whole. ‘Meta’ is Ancient Greek for ‘beyond’. Is there an objective reality? Are there laws of nature? Metaphysics answers these questions. Only then, can physics detail what that objective reality is and what those laws are. (Note: that was not how the word 'metaphysics' was coined, though it is an easy way to remember what the word actually means.)
Epistemology is the study of knowledge. What is true? What is untrue? How do we know what we know? Can we know anything?
Ethics is the study of good and evil. How do we distinguish the good from the evil? What is the standard of the good? Is ethics grounded in the supernatural or in the natural, in opinion (whether your own, some dictator’s, Society’s, or God’s) or in fact?
Politics is the study of society and government. What is the role of government? What should the laws be? Why do we need any laws?
Aesthetics is the study of art. What is art? What art is good art, and what art is bad art? What is the purpose of art?
Left: Plato (pic: © Marie-Lan Nguyen / Wikimedia Commons -- Creative Commons Attribution 2.5 Generic)
Right: Aristotle (pic: public domain)
Western philosophy, arguably, stems from the dispute between these two men.