Philosophy has almost as many definitions as there have been philosophers, both as a subject matter and an activity, and no simple definition can do it justice. The issue of the definition of philosophy is thus a controversial subject that is nowadays tackled by Metaphilosophy (or the philosophy of philosophy). The word is derived from the ancient Greek words philo-, to love or to befriend, and -sophia, wisdom. Modern usage of the term is much broader; the concept of philosophy encompasses all of knowledge and all that can be known, including the means by which such knowledge can be acquired. However, in the contemporary English-speaking academic world, the term is often used implicitly to refer to analytic philosophy and, in non-English speaking countries, it often refers implicitly to a different, European strain, continental philosophy. The ancient Greeks organized the subject into five basic categories: metaphysics, epistemology, ethics, politics and aesthetics. This organization of the subject is still largely in use in Western philosophy today.
Ethics – The study of the right, the good, and the valuable. Includes study of applied ethics.
Sexual ethics – The study of sexual relations rooted in particular behaviors and standards.
Logic – The study of good reasoning, by examining the validity of arguments and documenting their fallacies.
Metaphysics – traditional branch of philosophy concerned with explaining the fundamental nature of being and the world that encompasses it, although the term is not easily defined.
Atheism – the rejection of belief in the existence of deities. In a narrower sense, atheism is specifically the position that there are no deities.
Critical theory – examination and critique of society and culture, drawing from knowledge across the social sciences and humanities.
Humanism – approach in study, philosophy, worldview or practice that focuses on human values and concerns.
Transhumanism – international intellectual and cultural movement that affirms the possibility and desirability of fundamentally transforming the human condition by developing and making widely available technologies to eliminate aging and to greatly enhance human intellectual, physical, and psychological capacities. It is often abbreviated as H+ or h+.
Anarchism – political philosophy which considers the state undesirable, unnecessary, and harmful, and instead promotes a stateless society, or anarchy.
Libertarianism – political philosophy that advocates minimization of the government and maximization of individual liberty and political freedom.