Philosophy is the study of broad and basic issues, such as those concerning existence, reason, knowledge, values, the mind, and language. This is also the study of general and fundamental questions. In many cases, such issues are presented as problems that must be investigated or addressed. The word was supposedly created by Pythagoras (c. 570 – c. 495 BCE), according to some sources; however, others reject this claim, claiming that Pythagoreans were just claiming usage of a preexisting term. Philosophical approaches include inquiry, critical debate, logical argumentation, and systematic exposition, among other techniques.
Historical philosophy included all bodies of knowledge, and a philosopher was someone who practised what they preached about them. Natural philosophy was a broad term that included astronomy, medicine, and physics from the time of the ancient Greek philosopher Aristotle until the nineteenth century. A book of physics, such as Newton's Mathematical Principles of Natural Philosophy (1687), was subsequently classed as a book of mathematics.
Academic philosophy and other fields began to professionalise and specialise in the nineteenth century, as a result of the expansion of contemporary research institutions. Many fields of study that were historically included in philosophy have since been separated into distinct academic disciplines, notably the social sciences, which include subjects like psychological research and social work as well as linguistics and economics.
Modern academic philosophy is divided into several subfields, the most important of which are metaphysics, which is concerned with the nature of existence and reality at their most fundamental levels, epistemology, which studies the nature of knowledge and belief, ethics, which is concerned with the nature of moral value, and logic, which studies the rules of inference that allow one to derive conclusions from true premises. Philosophy of science, political philosophy, aesthetics, philosophy of language, and philosophy of mind are some of the other prominent subfields in philosophy.