A philosopher is a person with an extensive knowledge of philosophy who uses this knowledge in their work, typically to solve philosophical problems. Philosophy is concerned with studying the subject matter of fields such as aesthetics, ethics, epistemology, logic, metaphysics, as well as social philosophy and political philosophy.
There is a sense in which every human being is a philosopher, if we accept a very humanistic and generous interpretation. This is to say that every human being has a unique contribution of ideas to the society. However, a more generally accepted interpretation in academia is that a philosopher is one who has attained a Ph.D. in philosophy, teaches philosophy, has published literature in a field of philosophy in a peer-reviewed journal, or is widely accepted by other philosophers as a philosopher.