Philosophy (φιλοσοφία 'love of wisdom' in Ancient Greek) is a systematic study of general and fundamental questions concerning topics like existence reason knowledge value mind and language. It is a rational and critical inquiry that reflects on its own methods and assumptions.

Historically many of the individual sciences such as physics and psychology formed part of philosophy. However they are considered separate academic disciplines in the modern sense of the term. Influential traditions in the history of philosophy include Western Arabic–Persian Indian and Chinese philosophy. Western philosophy originated in Ancient Greece and covers a wide area of philosophical subfields. A central topic in Arabic–Persian philosophy is the relation between reason and revelation. Indian philosophy combines the spiritual problem of how to reach enlightenment with the exploration of the nature of reality and the ways of arriving at knowledge. Chinese philosophy focuses principally on practical issues in relation to right social conduct government and self-cultivation.

Major branches of philosophy are epistemology ethics logic and metaphysics. Epistemology studies what knowledge is and how to acquire it. Ethics investigates moral principles and what constitutes right conduct. Logic is the study of correct reasoning and explores how good arguments can be distinguished from bad ones. Metaphysics examines the most general features of reality existence objects and properties. Other subfields are aesthetics philosophy of language philosophy of mind philosophy of religion philosophy of science philosophy of mathematics philosophy of history and political philosophy. Within each branch there are competing schools of philosophy that promote different principles theories or methods.

Philosophers use a great variety of methods to arrive at philosophical knowledge. They include conceptual analysis reliance on common sense and intuitions use of thought experiments analysis of ordinary language description of experience and critical questioning. Philosophy is related to many other fields including the sciences mathematics business law and journalism. It provides an interdisciplinary perspective and studies the scope and fundamental concepts of these fields. It also investigates their methods and ethical implications.