What Is Philosophy? A Guide to the Discipline

Last verified: October 4, 2026. Philosophy is the systematic study of fundamental questions about knowledge, reality, value, reason, and the mind, pursued mainly by building and testing arguments rather than by running laboratory experiments or reading archives. It is one of the oldest scholarly disciplines and one of the least understood by people outside it, partly because the word is used loosely in everyday speech to mean a personal outlook (“my philosophy of life”) and partly because its questions overlap with those of nearly every other field. This guide explains what philosophy is as a research discipline, how its main branches divide the territory, what methods philosophers use, how the field relates to neighboring disciplines, what resources and professional bodies support it, how it is funded, and why it matters to anyone who works in research ethics or research administration.

What Is Philosophy?

The English word comes from the Greek philosophia, usually translated “love of wisdom.” Ancient Greek thinkers such as Socrates, Plato, and Aristotle are conventionally treated as foundational figures of the Western tradition, and the discipline has since developed through medieval, early modern, and contemporary periods, alongside rich traditions in other parts of the world, including Indian, Chinese, Islamic, and African philosophy. As a modern academic discipline, philosophy is best described by what philosophers do: they ask questions that cannot be settled by observation alone, state positions on those questions precisely, give reasons for them, and subject those reasons to the strongest available objections.

Three features set the discipline apart. First, its questions are often conceptual or normative: What is knowledge? What makes an action right? What is it for something to cause something else? Second, its standard of progress is argumentative: a position improves when its premises are clarified, its hidden assumptions exposed, and its answers to objections strengthened. Third, it is reflexive: philosophers also examine the assumptions of other fields, which is why there is a philosophy of science, of law, of history, of language, of mathematics, and of medicine. The relationship between those applied areas and the core of the discipline runs in both directions, because specific problems in other fields frequently sharpen general philosophical questions.

Philosophy is classified among the humanities. The National Endowment for the Humanities lists philosophy among the humanities disciplines, and the U.S. statute that created the agency names it as well. That classification has practical consequences for research administration: philosophers tend to work alone or in small groups, publish heavily in books and journal articles, and seek funding for release time, fellowships, and workshops rather than for equipment or large teams.

The Main Branches of Philosophy

Philosophers divide their field in several ways, and the divisions below are conventional rather than official. Individual philosophers often work across more than one branch, and many problems straddle them.

Metaphysics

Metaphysics studies the most general features of reality. Typical questions include what kinds of things exist, whether objects persist through change, what it is for one event to cause another, whether the future is open, what time and space are, and whether people have free will. Closely related is ontology, the study of what exists and how the things that exist are categorized. Researchers in other fields meet metaphysics whenever they ask what counts as a “species,” a “disease,” or a “gene.”

Epistemology

Epistemology is the study of knowledge and justified belief. It asks what knowledge is, how it differs from mere true belief, what counts as good evidence, whether and how skepticism can be answered, and how testimony, perception, memory, and reasoning each give us reasons to believe things. Epistemology is the branch most directly relevant to the practice of research, since questions about evidence, replication, expertise, and the reliability of methods are epistemological. Researchers writing a methods section often take an epistemological stance without naming it; the guide to the ontology and epistemology position statement shows how those commitments are stated in a thesis or protocol.

Logic

Logic is the study of correct reasoning. Formal logic develops precise systems for representing arguments and testing whether conclusions follow from premises. Philosophers also study informal reasoning, fallacies, and the differences between deductive, inductive, and abductive inference; see inductive vs. deductive vs. abductive reasoning for a plain-language comparison. Logic overlaps heavily with mathematics and computer science, and it supplies the vocabulary of validity and soundness that argument analysis in every other branch depends on.

Ethics

Ethics, or moral philosophy, studies how people ought to act and what makes actions, institutions, and characters good or bad. It is conventionally divided into three levels. Metaethics asks about the nature of moral claims: whether they can be true or false, and what they are about. Normative ethics develops general theories of right action; the best-known families are consequentialist theories, which judge actions by their outcomes, deontological theories, which stress duties and rights, and virtue ethics, which centers on character. Applied ethics brings these tools to concrete areas such as medicine, business, the environment, technology, and research. Several of those areas have their own pages on this site, including What Is Bioethics? and principles of research ethics.

Political and Legal Philosophy

Political philosophy examines the justification of political authority and the values that institutions should serve: justice, liberty, equality, legitimacy, rights, and the limits of state power. Legal philosophy (jurisprudence) asks what law is, how it relates to morality, and what makes legal reasoning sound. Both draw on ethics and on history, and both connect to the social sciences, particularly political science.

Aesthetics

Aesthetics studies art, beauty, taste, and the nature of aesthetic experience and judgment. It asks what makes something a work of art, whether aesthetic judgments can be objective, and how interpretation works. It is closely tied to the humanities fields that study creative works, such as literary studies and musicology.

Philosophy of Mind

Philosophy of mind studies the nature of mental states and their relation to the body: consciousness, perception, thought, intentionality, emotion, and the question of how mental phenomena relate to physical ones. It is one of the clearest points of contact between philosophy and empirical science, and it is a core contributor to cognitive science, along with psychology, neuroscience, linguistics, and computer science. Questions about whether artificial systems could have minds have made the area newly visible in public discussion of AI.

Other Major Areas

Many further fields are recognized as branches or sub-disciplines, including philosophy of language, philosophy of religion, history of philosophy, and the many “philosophy of” fields. The best-known applied example for readers of this site is the philosophy of science, which examines scientific method, explanation, evidence, and the nature of scientific knowledge, and is covered in its own guide. Religious studies is a separate field from philosophy of religion, though the two share questions and sources.

Methods of Philosophical Research

Philosophers do not share a single method, and methodological disagreement is itself a standing topic. Several techniques recur across the field.

• Argument analysis. The basic unit of philosophical work is the argument: a set of premises offered in support of a conclusion. Analysis involves reconstructing an argument in standard form, checking whether it is valid (the conclusion follows from the premises), assessing whether the premises are plausible, and considering objections and replies. Most journal articles in philosophy are organized around a thesis, an argument for it, and responses to the strongest objections.
• Conceptual analysis. Philosophers try to clarify a concept by stating the conditions under which it applies, then testing proposals against clear and borderline cases. Whether a proposed definition of “knowledge,” “cause,” or “fairness” survives a counterexample is a central form of evidence in the discipline, and critics debate how much such analysis can accomplish.
• Thought experiments. A thought experiment describes an imagined scenario and asks what we should conclude about it. They are used to isolate a variable, test a principle, or expose a tension in a theory. Because the scenario is stipulated rather than observed, the method depends on shared judgments about the case, which is what makes it both powerful and contestable.
• Appeal to intuitions and reflective equilibrium. Philosophers often treat considered judgments about particular cases as data, and then adjust general principles and particular judgments against each other until they cohere.
• Close reading and historical interpretation. Historians of philosophy read and interpret primary texts in their languages and contexts, using methods shared with history and philology.
• Formal modeling. In logic, decision theory, formal epistemology, and philosophy of language, philosophers use mathematical and logical models to state and test ideas precisely.

Experimental Philosophy

One notable development is experimental philosophy, often abbreviated x-phi. The Stanford Encyclopedia of Philosophy describes it as a methodologically naturalist approach to philosophy distinguished by practitioners employing empirical methods for philosophical purposes, using systematic empirical observation to test empirical claims that arise in the course of philosophical theorizing. According to the same entry, the most common technique is the questionnaire built around short vignettes that gather people’s judgments about cases, and researchers increasingly use corpus-linguistic methods as well as behavioral experiments, developmental studies, and bibliometric analyses. Experimental philosophy is a minority approach and remains debated within the field, including over what survey responses can show about philosophical questions. For research administrators, the practical point is that such studies often involve human participants and can require ethics review in the same way as any survey-based project, a topic taken up below.

How Philosophy Relates to Other Disciplines

Philosophy shares questions with many fields and has produced several disciplines that now operate independently. Natural science was historically part of philosophy, and the boundary remains permeable: philosophy of physics, philosophy of biology, and philosophy of mind all work in close contact with the corresponding sciences. Logic runs into mathematics and computer science. Ethics and political philosophy run into law, public policy, and economics. Aesthetics and history of philosophy run into the humanities. Because of this, philosophical training is a common route into interdisciplinary work, including bioethics, technology ethics, and AI governance.

It helps to distinguish philosophy from two neighbors. Compared with history, which reconstructs and interprets the past from surviving evidence, philosophy mainly evaluates reasons and concepts, though the history of philosophy is a field of its own. Compared with the empirical sciences, philosophy does not usually generate new data, but it examines what data mean, how theories relate to evidence, and what the terms of a science commit it to.

Research Resources and Professional Bodies

PhilPapers

The main discovery tool for philosophy literature is PhilPapers (philpapers.org). Its own “about” page describes it as a comprehensive index of the research literature in philosophy, run by two general editors, David Bourget and David Chalmers, with roughly 400 appointed academics serving as area editors who maintain particular topic categories. The page reports an index of more than three million books and articles, organized into thousands of topics, and states that the project is self-funded through subscriptions. It also hosts an open-access archive, PhilArchive, and related services for events, jobs, and researcher profiles. These figures come from PhilPapers’ description of itself on the date above and change as the index grows. For anyone searching a philosophical literature, the structured topic categories are often more useful than a general search engine because they group work by problem rather than by keyword.

The American Philosophical Association

The American Philosophical Association (APA) is the main professional association for philosophers in the United States. It is not to be confused with the American Psychological Association, which shares the abbreviation and publishes the widely used APA citation style; philosophers typically follow the style prescribed by the journal or press they submit to. The association’s website, apaonline.org, is the place to look for its current meetings, committees, job listings, statements on professional practice, and publications. Details such as founding date, divisional structure, and membership figures should be taken from the association directly rather than from secondary summaries, and this guide does not restate them.

Journals and Reference Works

Philosophy publishes through a mixture of generalist journals, specialist journals for each branch, edited volumes, and monographs from academic presses. Two free reference works are widely used and are written by specialists: the Stanford Encyclopedia of Philosophy and the Internet Encyclopedia of Philosophy. Many journals use anonymized review, a practice discussed in the comparison of single-blind, double-blind, and open peer review. Authorship norms in philosophy also differ from laboratory science: single-authored work is common, and contribution statements are rarer, which matters when a philosopher joins a funded interdisciplinary team (see single-author humanities vs. multi-author STEM authorship criteria).

Training and Careers

Philosophy is taught at the undergraduate level as a major or minor and at the graduate level through master’s and doctoral programs. In many countries the doctorate is the usual qualification for an academic career, which centers on teaching, research, and service. Graduates also work in law, government, publishing, technology, health care, and nonprofits, using the discipline’s training in analysis and writing. Job-market conditions for tenure-track academic positions are tight in many humanities fields, so applicants should consult current data from the relevant professional association rather than rely on general claims. Early-career researchers preparing application materials may find the guide to a research statement for a faculty application and the dictionary entry for a teaching statement useful.

How Philosophy Research Is Funded

Funding for philosophy is smaller in scale than for laboratory fields and comes from a mix of sources: university research leave and internal grants, national humanities agencies, private foundations, and, increasingly, interdisciplinary programs where philosophers work on ethics, technology, or the foundations of science.

• National Endowment for the Humanities (NEH). The NEH describes itself as the only U.S. federal agency dedicated to funding the humanities. It was created in 1965 by the National Foundation for the Arts and Humanities Act (P.L. 89-209), and it states that it has awarded more than $6 billion in grants since its creation. Its own materials name philosophy among the humanities subjects. Program names, deadlines, and award sizes change often, so applicants should check the current listings on neh.gov before planning around any program.
• John Templeton Foundation. The foundation, established in 1987, lists funding areas that include Religion, Science, and Society, along with Life Sciences, Mathematical and Physical Sciences, and Character Virtue Development. Much of its philosophy-related funding sits at the intersection of philosophy, science, and religion. See the guide to John Templeton Foundation research grants.
• Private humanities funders. Foundations such as the Andrew W. Mellon Foundation support humanities research and infrastructure; see Andrew W. Mellon Foundation humanities and arts research funding.
• Interdisciplinary and mission-driven programs. Ethics, technology, and AI governance programs at governments and foundations often seek philosophical expertise on a project team. In these settings a philosopher is commonly a co-investigator rather than the lead, which affects budgeting and authorship planning.

Philosophy and Research Ethics

Philosophy and research administration meet most directly in research ethics. The principles that govern human-subjects research are philosophical in origin and in justification. The Belmont Report principles of respect for persons, beneficence, and justice are moral principles drawn from the tradition of normative ethics and applied to the conduct of research; the report itself is defined in the Belmont Report dictionary entry. When an institutional review board weighs risks against benefits or judges whether consent is adequate, it is applying ethical reasoning of the kind philosophers study. The field of bioethics sits at the meeting point of philosophy, medicine, and law, and philosophers take part in ethics committees and policy bodies.

Philosophers can also be the investigators whose projects need review. A study that surveys participants about their moral judgments, as in much experimental philosophy, can fall under human-subjects regulations, while a purely conceptual or text-based project generally does not involve human participants at all. Where the line falls depends on the institution’s definition; see the definition of human subjects research and the guide to the principles of informed consent. The practical advice for administrators is to ask what the project actually does: archive-based and argument-based scholarship rarely needs review, while surveys, interviews, and behavioral experiments often do.

Frequently Asked Questions

What is philosophy in simple terms?

Philosophy is the careful, argument-based study of basic questions about what exists, what we can know, how we should act, how we should reason, and what minds are.

What are the main branches of philosophy?

The conventional divisions are metaphysics, epistemology, logic, ethics, political and legal philosophy, aesthetics, and philosophy of mind, along with history of philosophy and many “philosophy of” areas such as philosophy of language and philosophy of science.

What methods do philosophers use?

The most common are argument analysis, conceptual analysis, thought experiments, and reflective equilibrium, with close reading in the history of philosophy and formal modeling in logic and decision theory. Experimental philosophy adds empirical methods such as vignette surveys.

Is philosophy a science?

It is usually classed with the humanities, although it has close ties to science, logic, and mathematics. Some areas, such as philosophy of mind and experimental philosophy, work directly with empirical findings. See What Is Philosophy of Science? for how the discipline examines science itself.

Where do I search for philosophy research?

PhilPapers is the main specialist index. The Stanford Encyclopedia of Philosophy and Internet Encyclopedia of Philosophy provide expert overviews of specific topics.

Who funds philosophy research?

Universities, national humanities agencies such as the NEH, private foundations such as the John Templeton Foundation and the Andrew W. Mellon Foundation, and interdisciplinary programs in ethics and technology.

Does philosophy research need IRB review?

Argument-based and text-based scholarship generally does not involve human subjects. Projects that collect data from people, such as experimental philosophy surveys, may. Confirm with your institution’s review board, as definitions vary.

How is the American Philosophical Association different from the American Psychological Association?

They are separate organizations that share the initials APA. The Psychological Association publishes the APA citation style; the Philosophical Association is the professional body for philosophers in the United States.