An argument put forward by the first-century Pyrrhonist philosopher Agrippa for global skepticism about justification (and hence knowledge). This argument begins with the observation that, for a belief B to be justified, the chain of reasons ultimately leading to B must have one of three possible structures: the chain is either (a) finite and linear, (b) circular, or (c) infinite. The next step is to argue that each possible structure is problematic, then draw the conclusion that there is no possible way for a belief to be justified.

Agrippan trilemma

Epistemology, as the branch of philosophy that studies knowledge, has many specific terms. Here's a very useful glossary I found as part of my research for evolving Product Discovery concepts.

192 Terms in Epistemology 💡

Knowledge that is dependent on, or gained through, sense experience. A posteriori truths are truths known after experience.

a posteriori knowledge

A type of reasoning that attempts to form the best explanation of available data.

abduction

ability (procedural) knowledge

The attachment of meaning to a perceptual input based on our past and present experiences and concepts.

apperception

The “turn,” or major shift, among many epistemologists toward an emphasis on real-world applications (e.g., in politics, education, and everyday life).

applied turn

Ignoring a prior probability (or base rate) when determining a posterior probability.

base-rate fallacy

A belief that is not formed on the basis of any other belief(s).

basic belief

A formula in probability theory attributed to Reverend Thomas Bayes. The formula is used by Bayesians to describe how to update the probability of a hypothesis H given new evidence E:P(H|E) = [{P(E|H) ∙ P(H)}/P(E)], where P(E) ≠ 0.

Bayes’s theorem

The study of knowledge and justified belief within a degreed framework using formal methods, especially probability theory with emphasis on Bayes’s theorem.

In the context of this book (unless otherwise specified), “belief” refers to “belief-that,” which is the acceptance of a proposition’s truth. In other contexts, “belief” can refer to “belief-in,” which need not have a proposition as its object (e.g., “I believe in you.”). In contrast to belief-that, belief-in is not purely cognitive but has an affective component (e.g., hope or trust).

belief

A form of reasoning in which the truth of the premises logically guarantees the truth of the conclusion.

deduction

The acceptance of a proposition’s truth.

belief-that

The view combining what strong foundationalists believe with the claim that non-foundational beliefs are justified only via deduction from justified foundational beliefs.

Cartesian foundationalism

The belief that the corresponding proposition is false.

disbelief

Stances on the truth value of a proposition (belief, disbelief, or suspension of judgment).

doxastic attitudes

“It is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence.” The principle as defended by W. K. Clifford is considered an impermissivist statement of an evidentialist ethics of belief.

Clifford’s principle

A set of bets that, when accepted, yields a guaranteed loss.

Dutch book

The study of the epistemic properties of groups and their beliefs.

collective epistemology

An idea formed by combining multiple simple ideas or impressions. For example, the complex idea “diamond street” is formed by putting simpler ideas into relation: a street made of diamonds.

complex idea

That which cancels justification (a justification defeater) or knowledge (a knowledge defeater).

A general idea of something which allows us to recognize it as belonging to a category, distinguish it from other things, and think about it. For example, to have the concept “table” is to be able to think about tables, distinguish them from other types of furniture, and recognize tables upon encountering them.

concept

A degree of confidence (or credence) that a person places in the truth of a proposition.

degree of belief

The breaking down of a concept into more basic conceptual components, arranged to form a definition.

In a disagreement about a proposition p, a person S1 conciliates when S1 changes their attitude toward p in the direction of S2’s attitude toward p.

conciliate

The view that whenever one discovers that an epistemic peer disagrees about some proposition p, one is justified in conciliating. So, for example, if S1 confidently believes p and discovers that their peer S2 believes p is false with the same degree of confidence, then S1 will be justified in decreasing their confidence about p.

conciliationism

A family of views about knowledge and the word “know.” According to contextualism, the standards required for you to count as knowing something vary from context to context. Contextualists often argue that skepticism is correct in some contexts but incorrect in other contexts. That is, in some contexts, the high standards required of knowledge by skeptics are appropriate, and so in those contexts we fail to know. But in other contexts, the standards required for knowledge are laxer, and there we can know many things.

contextualism

When applied to claims, statements, or propositions, the term “contingent” refers to that which is possibly true and possibly false, not necessary. For example, it is a contingent truth that crows are black, since they are black but could have been white. The claim that crows are white is a contingent falsehood, since it happens to be false but could have been true.

contingent

The view that a proposition is true when it corresponds to reality and false otherwise.

correspondence theory

credences

An argument showing that rational credences must adhere to the laws of probability (based on the premise that rationality requires avoiding Dutch books).

Dutch book argument

Based on observation or experience.

empirical

The philosophical position according to which all our beliefs and knowledge are based on experience. Empiricism is opposed to rationalism.

empiricism

The kind of justification necessary for knowledge, requiring good epistemic reasons.

epistemic justification

Any kind of luck that positively or negatively affects one’s epistemic status.

epistemic luck

The Greek word for “knowledge” or “understanding” from which the term “epistemology” derives.

epistêmê

Wrongdoing related to knowledge. This includes individual interpersonal interactions that demonstrate injustice, as well as larger structures of inequity in knowledge distribution or knowledge production sustained in institutions such as the legal system, medicine, and education.

epistemic injustice

The view that the aim of democracy is (in part) to favor a true outcome (with voting answering a question such as, “which candidate is best to lead?”).

epistemic democracy

Any practice that interferes with the inquiry of some or all persons, without their consent/consultation, for their own purported epistemic health or improvement.

Epistemic peers with respect to a proposition p are equally likely to believe the truth about p (i.e., each is just as unbiased, intelligent, sober, well-informed, etc.).

epistemic peer

Truth-indicative reasons—the kind necessary for epistemic justification.

epistemic reasons

An axiological thesis that denies the T-monist claim that the natural aim of belief is truth. To the pluralist, finding no straightforward hierarchy among epistemic goods suggests an un-unified order of values or even an array of epistemic goods.

epistemic value pluralism

The study of the aims of cognition, and the value of epistemic states (knowledge, understanding, belief, suspension, etc.) and standings (justified, unjustified, etc.).

epistemological axiology

Ways of knowing that resist the exclusive dominance of “mainstream” epistemologies and the unjust social power dynamics that those epistemologies tend to reflect and reinforce. Instead, epistemologies of resistance are structured to meet epistemic needs of marginalized people. They include but are not limited to feminist epistemologies.

epistemologies of resistance

The branch of philosophy traditionally defined as the study of knowledge. However, many epistemologists gradually deemphasized or abandoned the study of knowledge per se, focusing instead on other topics that nevertheless pertain to knowledge, even if only in some loose or indirect way. Expanding the traditional definition to accommodate this shift, epistemology can be understood as the study of the epistemic.

epistemology

The philosophical project of providing guidance for morally and intellectually responsible doxa (belief, opinion), including how one should respond to recognized peer disagreement.

ethics of belief

The information available to a person (an “indication of truth to a person”).

evidence

The principle that a body of evidence can support a range of attitudes toward a given proposition. RP denies rational uniqueness (RU).

Roughly, the principle that, whenever some person S1 has some evidence that S2 has some evidence in support of p, then S1 has some evidence in support of p.

evidence of evidence principle (EEP)

Epistemologists who think that justification is entirely a matter of a person’s evidence.

evidentialists

Epistemologists who think justification is a matter of which propositions provide the best explanations for a person.

explanationists

A feature of a hypothesis that improves its quality as an explanation of the available data (other things being equal). An example of such a feature is simplicity, according to Ockham’s razor. By contrast, an explanatory vice is a feature of a hypothesis that reduces its quality as an explanation (other things being equal). If simplicity is an explanatory virtue, then unnecessary complexity in a hypothesis is the corresponding explanatory vice.

explanatory virtue

The view that justification is contingent on features of a person’s mind plus features external to a person’s mind.

externalism

That which entails the truth of its propositional object.

factive

The view that knowledge-level justification (the level required for knowledge, which is perhaps more stringent than ordinary justification) does not entail truth.

fallibilism (about knowledge)

The view that justification does not entail truth.

A belief that is not formed on the basis of any other belief(s).

The “turn,” or major shift, among many epistemologists toward the use of “formal” methods (borrowed from linguistics, logic, and mathematics) in an effort to make the field more rigorous.

formal turn

The problem for process reliabilism of specifying the relevant process type for any given belief so that its justificatory status can be assessed.

generality problem

The kind of knowledge that requires more than mere correct opinion.

The problem of how to handle Gettier cases in the analysis of knowledge.

Gettier problem

Systematically undermining someone’s confidence in their own credibility by denying or minimizing their memories, feelings, or perceptions.

gaslighting

The denial that we have any knowledge, including the denial that we can know that skepticism is true.

global skepticism

The process of understanding and being understood; it’s how you turn the “raw data” of information into knowledge that has meaning.

A mental representation, including individual concepts (such as the concepts “fire” and “hot”) and the thoughts constructed therefrom (such as “the fire is hot”).

idea

A form of reasoning in which the truth of the premises makes probable the truth of the conclusion.

induction

An objection to (testimonial) reductionism. If reductionism is true, then young children are too cognitively unsophisticated to have testimonially justified beliefs. But it is obvious that young children have testimonially justified beliefs. Thus, reductionism is false.

infant/child objection (ICO)

Given that all else is equal, one should choose the hypothesis that best explains the evidence. One form of this can be justified by a comparative use of Bayes’s theorem. It is closely related to Ockham’s razor.

inference to the best explanation

The view that every justified belief is justified by an infinite number of appropriately structured, available reasons.

infinitism

The philosophical position, held by many rationalists, according to which we have certain ideas in our minds from birth, ideas which can be realized through reason.

innatism

A good intellectual trait, such as open-mindedness, intellectual humility, intellectual honesty, curiosity, or understanding.

intellectual virtues

The view that knowledge is justified true belief—a modern interpretation of Plato’s view.

JTB analysis

The view that knowledge is justified true belief plus some fourth condition to rule out Gettier cases (and perhaps lottery cases).

JTB+ account

justification

Something that prevents the satisfaction of what would otherwise (were there no defeater) satisfy an epistemic theory’s justification condition.

justification defeater

The view that knowledge is conceptually basic (and hence the starting point for epistemological theorizing), usually in conjunction with the claim that knowledge is of primary epistemic value (rather than, say, justification or warrant).

lightweight knowledge

The thesis, named after John Locke, which relates the all-or-nothing rationality of traditional epistemology to the degreed framework as follows: a belief is rational when the rational degree of belief is sufficiently high (i.e., above some specific threshold level).

Lockean thesis

Speech that is not strictly true (e.g., figurative, hyperbolic, approximate, or elliptical speech).

loose talk

Cases in which a justified belief is true on probabilistic grounds (often thought to be a counterexample to the JTB analysis).

lottery cases

One of the two divisions of human understanding made by David Hume. Our knowledge of matters of fact comes from observation or generalization from experiences. In other words, it is a posteriori. Because such truths are contingent, they are merely probable rather than certain.

matters of fact

When applied to claims, statements, or propositions, the term “necessary” refers to that which must be true. In other words, it is impossible for a necessary truth to be false. For example, it is a necessary truth that a triangle has three sides, which means that it is impossible for a triangle to have any other number of sides. The opposite of necessity is contingency.

necessary

A belief that is formed on the basis of at least one foundational (basic) belief.

non-basic belief

A belief that is formed on the basis of at least one foundational (basic) belief.

non-foundational belief

That which is immediately or directly presented to one’s awareness in perceptual experience (prior to attaching meaning or applying a concept in apperception).

percept

The view that sometimes someone S is justified in believing some testimony p, but S lacks testimony-independent evidence that the testimony is reliable.

A version of Bayesianism that requires credences to be represented and governed by objective probabilities.

Knowledge of what it’s like to have a given experience.

phenomenal knowledge

Typically written as P(H|E) in Bayes’s theorem, it is the result of conditionalizing a hypothesis H on an incoming piece of evidence E, read as “the probability of the hypothesis given the evidence.”

posterior probability

An umbrella term for forms of ignorance connected to social power. These may include (but are not limited to) White ignorance, male ignorance, straight ignorance, cisgender ignorance, rich ignorance, and abled ignorance.

The kind of justification provided by good pragmatic reasons.

pragmatic justification

Practical benefits of belief or action.

pragmatic reasons

Whatever is good enough, absent a defeater, to yield ultima facie justification (justification all things epistemically considered).

Typically written as P(H) in Bayes’s theorem, it is the probability of a hypothesis H before conditionalization on evidence. Bayesians take prior probabilities, or priors, to represent one’s initial degree of belief in H.

The view that credences should conform to the laws of probability.

probabilism

An objection to probabilism, according to which adherence to the laws of probability would require logical omniscience (knowledge of, or at least justified belief in, all logically necessary truths).

problem of logical omniscience

The objection that subjective Bayesianism places no rational constraint on priors (prior probabilities).