Philosophy key terms

Knowledge or justification that is independent of sensory experience, derived instead from reason or conceptual analysis. Contrasted with a posteriori knowledge, which depends on empirical observation.

Knowledge or justification that depends on sensory experience or empirical evidence. For example, the claim that water boils at 100°C is known a posteriori.

The contrast between statements true by virtue of meaning alone (analytic, e.g., 'All bachelors are unmarried') and statements whose truth depends on how the world is (synthetic, e.g., 'All bachelors are tall').

The epistemological view that all knowledge derives from sensory experience. Classical empiricists include Locke, Berkeley, and Hume, who denied innate ideas.

The epistemological view that reason, independent of experience, is the primary source of knowledge. Associated with Descartes, Spinoza, and Leibniz, who emphasized innate ideas and deductive method.

The philosophical position that questions the possibility of certain knowledge. Global skepticism doubts all claims; local skepticism doubts specific domains, such as knowledge of other minds.

Descartes' method of suspending judgment about anything that can be doubted, in order to find an indubitable foundation for knowledge. It leads to the cogito: 'I think, therefore I am.'

Latin for 'I think, therefore I am.' Descartes' first certainty, which survives radical doubt because even a deceiving demon cannot make him mistaken about his own existence as a thinking thing.

Hume's challenge that inductive reasoning-inferring future regularities from past observations-cannot be justified by reason or experience without circularity. It questions whether we can rationally predict the future.

A 20th-century movement, especially the Vienna Circle, holding that meaningful statements are either analytic or empirically verifiable. It rejected metaphysics as meaningless and influenced philosophy of science.

The doctrine that a statement is meaningful only if it can be empirically verified or is analytic. Central to logical positivism, it faced self-referential difficulties because the principle itself is not verifiable.

A consequentialist ethical theory holding that the right action maximizes overall well-being or utility. Classical versions by Bentham and Mill focus on pleasure or happiness.

Kant's supreme moral principle, binding unconditionally. Its formula of universal law requires acting only on maxims that could be willed as universal laws; the humanity formula treats persons as ends in themselves.

An ethical theory that judges actions by their conformity to duties or rules, rather than by their consequences. Kant's ethics is the paradigm, emphasizing respect for persons and moral obligations.

An approach to ethics that focuses on character traits and what makes a good person, rather than on rules or consequences. Rooted in Aristotle's eudaimonia and the doctrine of the mean.

Aristotle's term for human flourishing or happiness, the ultimate goal of life. It is achieved through virtuous activity in accordance with reason, not merely through pleasure or wealth.

Aristotle's ethical principle that virtue lies between two vices: one of excess and one of deficiency. For example, courage is the mean between recklessness and cowardice.

The class of ethical theories that evaluate actions solely by their outcomes. Utilitarianism is the most prominent form, but consequentialism also includes theories focused on other goods.

In logic, a property of arguments where, if the premises are true, the conclusion must be true. Validity concerns the logical form, not the actual truth of the premises.

A property of arguments that are both valid and have all true premises. Soundness guarantees the truth of the conclusion.

A valid argument form: If P, then Q; P; therefore Q. It affirms the antecedent and is a basic rule of inference.

A valid argument form: If P, then Q; not Q; therefore not P. It denies the consequent and is a standard rule of inference.

A deductive argument with two premises and a conclusion, typically in categorical form. Aristotle's categorical syllogisms are the classical model.

A common error in reasoning that renders an argument invalid or weak. Examples include ad hominem, begging the question, and equivocation.

A fallacy in which an argument assumes the very conclusion it aims to prove, often by restating the conclusion in a premise. Also called circular reasoning.

Plato's theory that abstract, perfect entities (Forms) exist independently of the sensible world. Particular things are imperfect copies that participate in the Forms.

Plato's image in the Republic illustrating ignorance and enlightenment. Prisoners mistake shadows for reality; the philosopher escapes to the Forms and returns to educate others.

Aristotle's doctrine that every physical substance is a compound of matter (hyle) and form (morphe). Form gives matter its determinate nature and is not a separate Platonic entity.

Aristotle's four explanations of change: material (what something is made of), formal (its essence), efficient (what brings it about), and final (its purpose or end).

Short for Descartes' 'cogito ergo sum' ('I think, therefore I am'), the foundational certainty that survives methodological doubt and grounds his epistemology.

A political theory that legitimate authority arises from an agreement among individuals to form a society. Hobbes, Locke, and Rousseau offer influential but differing versions.

A hypothetical condition of humanity before political society, used by social contract theorists to justify government. Hobbes depicts it as a war of all against all; Locke as relatively peaceful.

Rousseau's concept of the collective will of a people aimed at the common good, distinct from the sum of individual private wills. It grounds legitimate sovereignty in The Social Contract.

Rawls' device for choosing principles of justice: parties decide behind a veil that hides their social position, talents, and conception of the good, ensuring impartiality.

Rawls' hypothetical situation in which free and equal persons, behind a veil of ignorance, agree on principles of justice for the basic structure of society.

Rawls' theory that justice is the first virtue of social institutions. Its two principles guarantee equal basic liberties and regulate social and economic inequalities to benefit the least advantaged.

In Kant, a judgement of taste that is subjective yet claims universal agreement, based on a feeling of pleasure or displeasure rather than concepts. It concerns the beautiful and the sublime.

An aesthetic experience of overwhelming greatness or power, which initially frustrates imagination but pleases through reason's sense of superiority. Kant distinguishes the mathematical and dynamical sublime.

The subjective, qualitative character of conscious experience-what it is like to see red or taste coffee. Qualia pose a challenge to physicalist accounts of mind.

The view that mind and body are distinct kinds of substance or property. Substance dualism, associated with Descartes, holds that the mind is immaterial and the body material.

A theory of mind holding that mental states are defined by their causal roles-their relations to inputs, outputs, and other mental states-rather than by their physical composition.