Also called abductive logic, abductive reasoning, or abductive inference. A type of logical reasoning in which one reasons to the best explanation of a phenomenon. This form of logic is descriptive of the type of reasoning employed in reaching a scientific hypothesis. Abductive logic has not achieved widespread acceptance as a distinct form of logical reasoning independent of deduction and induction. Many philosophers and logicians recognize it simply as a form of induction.

A statement is an analytic truth if it is necessarily true or true by definition. For example, “All bachelors are married.”

Presuming, favoring, oriented toward male views and values.

After experience. A posteriori typically refers to knowledge gained from sensory experience.

Prior to experience. A priori typically refers to knowledge (especially knowledge of logic and mathematics) that is not due to experience.

Latin for “all things being equal.” A qualification invoked in order to mentally strip away uncontrollable variables.

The quality of a good inductive argument such that (a) it is strong and (b) all its premises are true.

The statement of an argument that premises are meant to provide reasons or evidence for belief.

Logically, the quality of two statements such that there is no logical relationship between them. Epistemologically, the term can refer to statements that are true or false dependent on actual states of the world. Metaphysically, the term may refer to an object that does not exist of necessity.

A movement in philosophy and social science, influenced largely by the works of Marx and Freud, that asserts that philosophy and social science should work to free people from political and other forms of oppression.

Also called deduction, deductive logic, deductive reasoning, or deductive inference. A form of logic in which one claims to argue to a certainty.

The acceptance of beliefs without critical thought. The irrational, absolutist commitment to a belief system.

A metaphysical position that holds that there are two basic, irreducible substances in the universe, of which everything is composed. The most well-known form of dualism is mind–body dualism, particularly that of Descartes. According to the theory of mind–body dualism, everything is made of immaterial (nonphysical) mind or spirit (souls/minds, ideas, mental states, etc.) or material (physical) body (human bodies, trees, stars, rocks, mountains, etc.) or some combination of the two (persons).

A method of inquiry associated with Socrates in which discussants of various views test one another’s claims through critical questioning.

An epistemological position in which knowledge claims are based on and confirmed by sensory experience, usually posed against rationalism. Empiricism is sometimes used to refer generally to any epistemological position or theory that focuses on or affirms the authority of sensory experience. In this way, empiricism could be used to describe the theories of philosophers dating back to Aristotle. Sometimes, though, it is used to describe more narrowly the empiricism of a group of modern philosophers known as British Empiricists (sometimes called Classical Empiricists) and later 19th- and 20th-century philosophers who were influenced by their specific approach to empiricism. The three primary British Empiricists were John Locke (1632–1704), George Berkeley (1685–1753), and David Hume (1711–1776). The school of philosophy most influenced by this approach to empiricism was logical positivism.

In Aristotelian philosophy, a force within objects (both living and inanimate) that leads them to their proper, natural place.

The branch of philosophy that studies the source, nature, scope, and confirmation of knowledge and knowledge claims.

Latin term for a phenomenon to be explained.

Latin term for the explanation given for an explanandum.

An approach to social science that presumes that understanding can be attained by searching for manifest and latent functions of human and social action.

Presuming, favoring, oriented toward female views and values.

Relating to interpretation. Originally, hermeneutic referred to the study of biblical interpretation. Later it was expanded to refer to the study of interpretation in general. It also refers to a philosophical and social scientific approach that focuses on the interpretation of human action in the context of social rules.

The view that understanding can only be attained from a perspective of wholes. Things are more than the sum of their parts.

A common philosophical meaning of the word idea is any content of the mind, including thoughts, perceptions, doubts, wishes, and so on.

A metaphysical position in which it is held that everything is composed of immaterial or spiritual substance. According to idealists, matter does not in fact exist. This does not mean that the table in front of you is not real. It is real as an “idea” (a mental object), but not as a physical object.

Logically, the quality of a statement (or statements) that its truth guarantees the truth of an implied statement.

Logically, the quality of a statement (or statements) that its truth guarantees the falsity of the incompatible statement.

Also called induction, inductive reasoning, inductive logic, or inductive inference. A form of logic in which one claims to argue to a probability. Three common types of inductive argumentation are generalization, analogies, and causal arguments.

Also, inferential reasoning. The mental act of starting with knowledge claims that are known or assumed to be true and drawing further knowledge claims from those. A very simple example is Aristotle’s famous syllogism:

From the first two statements (the premises) we can infer the third statement (the conclusion).

The view that cognitive tools such as mathematics or scientific theories are just tools (instruments) for achieving specific goals like predicting phenomena and are not necessarily reflective of reality.

Referring to elements, perceptions, and beliefs of the mind; that which is subject to interpretation.

The quality of a bad deductive argument, such that the premises do not guarantee the truth of the conclusion. It is possible to have all true premises but a false conclusion.

The branch of philosophy that studies inferential reasoning. Logic is traditionally divided into deductive logic and inductive logic, though the American philosopher Charles Sanders Peirce (1839–1914) introduced a third type, abductive logic. The first philosopher in the West to systematize logic was Aristotle, whose system dominated logic and logical studies until the development of propositional logic in the late 19th century.

A school of philosophical thought that grew out of the intellectual movement known as the Vienna Circle. Logical positivists were especially interested in the philosophical study of science. They saw science as merely empirical study structured and justified logically.

The metaphysical position that holds that all that exists is made of matter or physical substance. Souls, spirits, and immaterial objects in general do not exist. Minds are explained as part of or processes of the physical, organic brain.

That branch of philosophy that studies ultimate reality, what the nature and essence of existence is, what things and types of things actually exist, and in what nature they exist.

The metaphysical position that holds that only one type of irreducible substance exists. Everything in the universe is in fact made of this one substance. Many of the earliest philosophers expressed a monist view, asserting the underlying reality to be water (Thales), air (Anaximenes), or fire (Heraclitus). The modern world generally recognizes two forms of monism: materialism and idealism—although there are numerous varieties of those views.

The view that our common sense beliefs and perceptions accurately reflect the world.

Law like, pertaining to laws and values, prescriptive as opposed to descriptive. From the Ancient Greek nomos, which means law or custom.

Relating to knowledge of independent reality; distinct and unaffected by specific, personal, invested views.

A term used by Thomas Kuhn to refer to the broad conceptual frameworks that shape and inform the beliefs, views, and research of scientists.

A fundamental change in worldview.

An empirical view in which the reality of physical objects is reduced to their perceptual existence.

A movement in philosophy and social science that focuses on inner subjective experience to attain understanding.

A philosophical position on science attributed to French philosopher Auguste Comte (1798–1857). Positivism emphasized empirical study as the only means of acquiring knowledge. Comte particularly advocated this approach for the social sciences. Comte’s use of this term was adopted later by the Logical Positivists of the 20th century.

A broad philosophical, literary, artistic, and cultural movement in which the presumptions of modernism are powerfully criticized and questioned.

A philosophical school originally associated with the American philosophers Charles Sanders Peirce (1839–1914), William James (1842–1910), and John Dewey (1859–1952). Later pragmatists include W. V. O Quine (1908–2000), Richard Rorty (1931–2007), Hilary Putnam (1926–), and Ian Hacking (1936–). Pragmatists generally eschew metaphysical flights and attempt to connect our philosophical beliefs and inquiries to practical life.

Sometimes premiss. A statement in an argument intended to provide evidence or reason to believe that the conclusion of the argument is true.

An approach to social science in which it is presumed that humans are essentially rational and will generally make rational, self-interested decisions.

An epistemological position in which knowledge claims are based on and confirmed by the mind and the mental processes of the mind, usually posed against empiricism. Rationalism is sometimes used to refer generally to any epistemological position or theory that focuses on or affirms the epistemological authority of the mind. In this way, “rationalism” could be used to describe the theories of philosophers dating back to Plato. Sometimes it is used to describe any philosophical position with an emphasis on the employment of reason, especially as opposed to recognition of nonrational (especially emotional) elements of human nature and thought. Sometimes, though, it is used to describe more narrowly the rationalism of a group of modern philosophers known as Continental Rationalists. The three primary Continental Rationalists were René Descartes (1596–1650), Gottfried Leibniz (1646–1716), and Baruch Spinoza (1632–1677). Rationalists tend to hold a very high standard of knowledge, usually with models of epistemic certainty being logic (deductive) and mathematics.

A type of argument in which another’s claim or argument is criticized by showing that it logically leads to an absurd or otherwise untenable conclusion.

The view that understanding comes from breaking entities down to their constituent parts. Things are no more than the sum of their parts.

The metaphysical view that science accurately informs us about the state of the world.

The view that all one can know to exist, or even all that does exist, is one’s own self or mind. From the Latin solus (only or alone) and ipse (self), so literally, “alone-self-ism.”

A quality of a good deductive argument such that (a) it is valid and (b) all the premises are true. Logically, then, the conclusion must also be true. This means that it is possible for an argument to be valid but not sound, but not possible for an argument to be sound but not valid.

Also, proposition, claim, or assertion. A declarative sentence, the kind of sentence that can be true or false. More technically, “statement” refers to the thought behind the declarative sentence. For example:

Numbers 3 and 4 are in fact the same statement expressed in different sentences.

Qualitative assessments of inductive arguments. Strong arguments are ones in which the premises provide good support for the conclusion. Weak arguments are ones in which the premises provide poor or little support for the conclusion.

Relating to the internal workings of the mind, affected by specific, personal, sometimes invested views.

A statement that is not analytically true or analytically false. Its truth is dependent on contingent states of the world as it brings together (synthesizes) separate, distinct concepts.

From the Ancient Greek telos, which means end, purpose, or goal. This is the ancient and medieval worldview that all things in the world have an inherent purpose. For example, rain falls not due to meteorological laws, but in order to nourish plants and animals.

Colloquially, people use the word “valid” in a nebulous manner as a general synonym for good. In deductive logic, it is a technical term that refers to the quality of a deductive argument such that if the premises are true, then the conclusion must be true. Another way of saying this is that the truth of the premises guarantees the truth of the conclusion.