Aristotle statuePhilosophy—the love of wisdom—is an academic discipline dedicated to the study of knowledge and is one of the oldest academic pursuits, dating back thousands of years. Many disciplines that we now recognize as distinct from philosophy—including biology, psychology, physics, math, and numerous others—were once studied by philosophers. Aristotle, for example, is recognized as a founder of biology, and authored several volumes on taxonomy and animal biology.

What Is Philosophy?

The precise definition of philosophy is an ongoing subject of philosophical debate. Because philosophy concerns itself with broad inquiries into life, being, and knowledge, it touches almost every academic discipline. As a result, many topics that philosophy focuses on eventually become specialized disciplines, distinct from philosophy. For example, Sir Isaac Newton’s Mathematical Principles of Natural Philosophy presented many of the physical laws we still use today, and it was originally intended as a work of philosophy. The book helped spur the creation of physics, though, and physics is now generally recognized as an area of knowledge that is separate from philosophy.

Some philosophers have argued that all knowledge is classified as philosophy in its early stages and that as the knowledge becomes specialized, it gains its own discipline. Given this ongoing segmentation of knowledge, it’s not surprising that even philosophers are unable to agree on what philosophy is or should do.

Various philosophers have suggested several roles for philosophy, including:

  • Defining the scope of other domains of knowledge. For example, philosophy could be useful at helping scientists draw a line between science and pseudoscience.
  • Ensuring that questions of knowledge are properly framed. A researcher who asks if dogs are more emotional than cats might benefit from the help of a philosopher who can assist in defining emotion and determining whether it is possible to know and evaluate the emotions of another being.
  • Uncovering new domains of knowledge. Philosophy is sometimes built upon speculation coupled with logic. This approach provides a strong framework for creating new areas of knowledge. As empirical evidence and scientific research become readily available, these disciplines can then separate themselves from philosophy.
  • Determining what constitutes a good life. Because philosophy is enmeshed with so many different areas of knowledge, some philosophers argue that the discipline is uniquely positioned to help people solve problems of religion, happiness, morality, and meaning.

Branches of Philosophy

Philosophy is a dynamic, evolving discipline, which means that every generation defines what does and does not constitute philosophy slightly differently. Very broadly speaking, philosophy can be divided into the following sub-disciplines:

  • Epistemology: The study of knowledge. This branch of philosophy examines what we can and can’t know and how we can most effectively gain more knowledge. The philosophy of science is one of many areas of study within the field of epistemology.
  • Logic: The study of reasoning. Logicians analyze sentence structure, define fallacies, and provide guidance on how to form well-reasoned arguments. Within the field of logic, there are two approaches to reasoning—deductive and inductive reasoning. Some philosophers argue that inductive reasoning is logically problematic and can lead to incorrect information. For example, if you believe that the sun will rise tomorrow because it rose today, you are using inductive reasoning—reasoning based on evidence and experience rather than logic.
  • Ethics: The study of how to live a good and moral life. It includes sub-disciplines, such as legal and political philosophy. Immanuel Kant addressed many areas of philosophy, but is well known for his ethical categorical imperative. This law argues that (a) people must be treated as ends in themselves, not means to an end; and (b) we should act in ways that can be universalized. For example, if everyone lied all the time, even truths would be perceived as lies, and communication would then prove unreliable and ineffective.
  • Metaphysics: The study of reality. This field can be further subdivided into cosmology, which devotes itself to the study of the universe and ontology, which studies the nature of being. Some religious philosophy addresses metaphysical issues. 

There are many other pursuits within the field of philosophy, including philosophy of law, philosophy of religion, and linguistic philosophy. Many of these domains of knowledge cut across the borders of several disciplines in philosophy. 

Philosophy and Psychology

In the early days of psychology, many philosophers contributed to the field, and many psychologists made philosophical claims. These interdisciplinary experts include Sigmund Freud, William James, Aristotle, Friedrich Nietzsche, and Arthur Schopenhauer. 

Philosophy also plays a key role in defining and deepening psychological questions. Philosophy of science, for example, dedicates itself to determining what counts as scientific knowledge, what evidence is sufficient to prove a hypothesis, and how we can really know anything. This has direct bearing on psychological experiments and claims. 

Psychology and the Philosophy of Mind

One area of philosophy in particular, philosophy of mind, has contributed much to psychology. As the name implies, philosophy of mind studies mental constructs and psychological states. It also examines how we can ever know that another person is conscious or has a mind. 

The most central problem in philosophy of mind is the mind-body problem. Originally presented by Rene Descartes, the mind-body problem attempts to find the connection between mental states and biological processes. Contemporary scientists believe that subjective experience originates in the brain, but have not yet fully accounted for how a physical entity such as the brain can give rise to subjective experiences and consciousness. Raymond Tallis, a philosopher and neuroscientist, has published several books on this very issue. 

Important figures in the philosophy of mind include David Chalmers, B.F. Skinner, Douglas Hofstadter, Jerry Fodor, Thomas Nagel, Maurice Merleau-Ponty, Daniel Dennett, and John Rogers Searle. 


  1. Audi, R. (1995). The Cambridge dictionary of philosophy. Cambridge: Cambridge University Press.
  2. Honderich, T. (1995). The Oxford companion to philosophy. Oxford: Oxford University Press.
  3. Russell, B. (1945). A history of western philosophy, and its connection with political and social circumstances from the earliest times to the present day. New York, NY: Simon and Schuster.

Last Updated: 08-17-2015

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