Terms
Glossary
The words the debate about knowledge is conducted in, defined briefly and linked to the pages where they matter.
- Ad hoc
- Latin for "to this". An adjustment to a theory is ad hoc when it is made only to rescue the theory from a refutation and has no other consequence that could be tested.
- Anomaly
- A result that will not fit the accepted theory. For Kuhn, anomalies are set aside during normal science and bring on a crisis when enough of them accumulate.
- A priori
- Known independently of experience, as the truths of logic are usually held to be. Kant argued that some a priori truths, such as "every event has a cause", are also informative about the world.
- Bayes' theorem
- A theorem of probability that gives the probability of a hypothesis in the light of evidence, from the probability of the evidence if the hypothesis is true and the probability of the hypothesis beforehand.
- Bucket theory of the mind
- Popper's name for the view that the mind is an empty container that experience fills, with knowledge as what accumulates. He opposed it with the searchlight: observation directed by a prior question.
- Conjecture
- A guess: a theory proposed without proof or justification, to be tested and criticised. For Popper and Deutsch all knowledge begins and remains conjectural.
- Constructor
- In constructor theory, anything that can cause a transformation in other physical systems and keep its ability to do so again. Catalysts, engines and living cells are examples.
- Corroboration
- Popper's term for what a theory gains by surviving serious attempts to refute it. It is a record of past tests. It does not make the theory probable or justified.
- Credence
- A degree of belief, written as a number between 0 and 1.
- Critical rationalism
- Popper's philosophy: we cannot justify our theories, but we can criticise them rationally and prefer those that withstand criticism best. Deutsch's position is a development of it.
- Demarcation
- The problem of saying what separates empirical science from everything else. Popper's criterion is falsifiability.
- Empiricism
- The doctrine that all knowledge of the world comes from sense experience. Bacon, Locke and Hume are its classic figures; Quine a modern one.
- Epistemology
- The theory of knowledge: what it is, where it comes from and how it grows.
- Evolutionary epistemology
- The view that knowledge of every kind grows as species do, by variation and selective retention.
- Explanation
- A statement about what is there, what it does, and how and why. Deutsch holds that the aim of science is explanation, with prediction as a means of testing it.
- Fallibilism
- The view that any of our beliefs may be mistaken and that there are no authoritative sources of knowledge. It is not scepticism: fallibilists hold that knowledge exists and can be improved.
- Falsifiability
- A theory is falsifiable if some possible observation would contradict it. Popper made this the mark of empirical science.
- Foundationalism
- The view that knowledge must rest on a base of beliefs that need no further support, whether supplied by the senses or by reason.
- Gettier case
- A situation in which someone has a justified true belief that is not knowledge, because it is true by luck.
- Hard to vary
- Deutsch's criterion for a good explanation: its details cannot be changed without spoiling its account of what it explains. Myths fail the test; the axial-tilt theory of the seasons passes it.
- Holism
- The thesis that hypotheses are tested only in groups, so that a failed prediction does not show which of them is false. Also called the Duhem–Quine thesis.
- Idols of the mind
- Bacon's four sources of systematic error: those of human nature (the Tribe), of the individual (the Cave), of language (the Marketplace) and of philosophical systems (the Theatre).
- Incommensurability
- Kuhn's and Feyerabend's claim that rival paradigms share no common measure by which they can be compared point for point.
- Induction
- Supposed reasoning from observed cases to a general law or to unobserved cases: these swans are white, so all swans are white. Popper and Deutsch deny that any such form of reasoning exists.
- Instrumentalism
- The view that scientific theories are tools for predicting observations and make no claim about what really exists. Deutsch rejects it.
- Justification
- Whatever is supposed to show that a belief is true or probably true: evidence, proof, a reliable source. The central dispute on this site is whether knowledge needs it.
- Justified true belief
- The traditional analysis of knowledge, descended from Plato: you know something when you believe it, it is true, and you are justified in believing it.
- Justificationism
- The assumption that knowledge is belief that has been justified. Critical rationalists use the word for the tradition they reject.
- Münchhausen trilemma
- Hans Albert's name for the ancient sceptical argument that any attempt at justification ends in an infinite regress, a circle or an arbitrary stopping point.
- Naturalised epistemology
- Quine's proposal that the theory of knowledge should become part of empirical psychology, studying how people in fact arrive at their beliefs.
- Normal science
- Kuhn's term for routine research within an accepted paradigm, which extends it and does not question it.
- Paradigm
- For Kuhn, the shared theories, exemplary problems, methods and standards that define a scientific community's work at a given time.
- Prior
- In Bayesian reasoning, the credence given to a hypothesis before a piece of evidence is taken into account.
- Problem of induction
- Hume's problem: no argument can show that unobserved cases will resemble observed ones without assuming the very thing to be shown.
- Rationalism
- In its classical sense, the doctrine that reason alone, without the senses, is a source of knowledge about the world.
- Reach
- Deutsch's word for the ability of an explanation to solve problems beyond those it was created to solve.
- Research programme
- For Lakatos, a series of theories sharing a hard core of assumptions, protected by a belt of auxiliary hypotheses that is adjusted when predictions fail.
- Scepticism
- The view that knowledge is impossible, or that judgement should be suspended. The ancient Pyrrhonists arrived at it by showing that no belief can be justified.
- Tacit knowledge
- Knowledge that its holder cannot put fully into words, such as how to ride a bicycle or recognise a face. Deutsch's term for a similar idea is inexplicit knowledge.
- Theory-laden
- Observation is theory-laden because what we notice, and what we take it to be, depend on theories we already hold.
- Universal explainer
- Deutsch's term for a person: an entity able to create explanatory knowledge of any kind, limited only by the laws of physics.
- World 3
- Popper's name for the realm of objective contents of thought, such as theories, problems and arguments, as distinct from physical things (World 1) and mental states (World 2).