Philosophy

The branch of philosophy concerned with the nature, sources, and limits of knowledge. Epistemology asks what distinguishes justified belief from mere opinion, and whether certainty is attainable. Central debates include the nature of truth, the structure of justification, and the challenge of skepticism.

The branch of philosophy that investigates the fundamental nature of reality, including the relationship between mind and matter, substance and attribute, and potentiality and actuality. It addresses questions about what exists, the nature of time and space, causation, and personal identity.

The branch of philosophy dealing with questions of right and wrong, moral duty, and the good life. Ethics is divided into normative ethics (what we ought to do), metaethics (the nature of moral claims), and applied ethics (specific moral issues like euthanasia or war).

The study of valid reasoning, argumentation, and inference. Logic provides formal tools for distinguishing sound arguments from fallacious ones, and it underlies mathematics, computer science, and everyday critical thinking. It includes propositional logic, predicate logic, and modal logic.

A philosophical movement emphasizing individual existence, freedom, and choice. Existentialists argue that humans are not defined by a predetermined essence but instead create meaning through their actions and decisions. The movement grapples with anxiety, absurdity, authenticity, and the burden of radical freedom.

The epistemological theory that knowledge derives primarily from sensory experience. Empiricists argue that the mind begins as a blank slate and that all concepts and knowledge are ultimately grounded in observation and experiment, rejecting the notion of innate ideas.

The epistemological theory that reason, rather than sensory experience, is the primary source of knowledge. Rationalists hold that certain truths can be known a priori, through pure thought alone, and that the mind possesses innate ideas or structures that shape understanding.

An ethical theory holding that the morally right action is the one that produces the greatest good for the greatest number. Founded by Jeremy Bentham and refined by John Stuart Mill, utilitarianism evaluates actions solely by their consequences, specifically by the amount of happiness or well-being they produce.

Immanuel Kant's foundational principle of deontological ethics, which commands that one should act only according to rules that could be universalized without contradiction. Unlike hypothetical imperatives that depend on desires, the categorical imperative is an unconditional moral law binding on all rational beings.

A philosophical method and movement founded by Edmund Husserl that studies the structures of conscious experience from the first-person perspective. Phenomenology brackets assumptions about the external world to focus on how things appear to consciousness, examining intentionality, perception, and the lived experience of time and space.