3 markers

a posteriori 

Knowledge of propositions that can only be known to be true or false through sense experience. 

a priori

Knowledge of propositions that do not require (sense) experience to be known to be true or false.

ability (or skill) knowledge 

knowing ‘how’ to do something

acquaintance knowledge

Knowing ‘of’ someone or some place

analytic

A proposition that is true (or false) in virtue of the meanings of the words. For instance, ‘a bachelor is an unmarried man’ is analytically true

belief

Affirmation of, or conviction regarding, the truth of a proposition.

clear and distinct ideas (Descartes)

A clear idea is ‘present and accessible to the attentive mind’; a distinct idea is clear and also sharply separated from other ideas so that every part of it is clear.

cogito

‘I think, I am'. Descartes' first certain knowledge.

copy principle (Hume) 

All simple ideas are copies of impressions

direct realism

Physical objects exist independently of our minds and of our perceptions of them and the immediate objects of perception are mind-independent objects and their properties.

empirical 

Relating to or deriving from experience, especially sense experience, but also including experimental scientific investigation.

empiricism

The theory that there can be no a priori knowledge of synthetic propositions about the world (outside my mind)

epistemology

the study of knowledge and related concepts, including belief, justification, and certainty. It looks at the possibility and sources of knowledge

external world 

everything that exists outside of our minds

Gettier case/counter-example

A situation in which we have justified true belief, but not knowledge, because the belief is only accidentally true, given the evidence that justifies it.

hallucination 

A non-veridical perceptual experience that is not coherently connected with the rest of our perceptual experience. 

Hume’s ‘fork’ 

We can have knowledge of just two sorts of claim: the relations between ideas and matters of fact. Anything that ‘crosses the fork’ is not knowledge. 

idea 

An object of perception, thought, or understanding. Locke uses the term to refer to a complete thought 

(complex) idea 

an idea that is derived from two or more simple ideas.

(simple) idea

A single, uniform conception, with nothing distinguishable within it. 

Idealism (Berkeley’s) 

All that exists are minds and ideas. What we think of as physical objects are, in fact, bundles of ideas. The immediate objects of perception (ordinary objects such as tables, chairs etc.) are ideas, mind-dependent objects. Esse est percipi (aut percipere) – to be is to be perceived (or to perceive).

Illusion

A distortion of the senses such that what we perceive is different from what exists.

Impression

What we are immediately and directly aware of, which can either be impressions of ‘sensation’ (coming from the external world) or impressions of ‘reflection’ (coming from our own minds). Locke refers to these as simply ’sensations’.

indirect realism 

We perceive physical objects, which exist independently of the mind, indirectly via sense-data which are caused by and represent physical objects.

infallibilism

To be knowledge, a belief must be certain. If we can doubt a belief, then it is not certain, and so it is not knowledge. 

innate

Knowledge or ideas that are in some way built into the structure of the mind, rather than gained from sense experience. 

innatism

The theory that states certain concepts or knowledge are part of our minds rather than derived from sense experience. 

involuntary perception

A perception you have that you have no voluntary control over, you are passive in experiencing it. 

justification

What is offered as grounds for believing an assertion. 

lemma

A claim made part way through an argument. 

matters of fact

States of affairs, how the world is. According to Hume, they are known through experience and induction (a posteriori) and could be true or false (contingent).

mind-dependant

Depending on a mind for existence or definition, e.g. ideas are mind-dependent.

mind-independant

Not depending on a mind for existence or definition. According to realism in perception, physical objects are mind-independent; according to moral realism, moral properties are mind-independent (in some important way).

necessary condition

One proposition is a necessary condition of another when the second cannot be true while the first is false. For example, being a man is a necessary condition of being a bachelor, as if you are not a man you cannot be a bachelor.

no false lemmas

The 'no false lemmas' condition is sometimes added to the tripartite theory of knowledge and says that for something to count as knowledge it must be the case that you did not infer it from anything false. 

perceptual variation (argument from)

Against direct realism: Different people perceive the same physical object differently. Therefore, what each person perceives is how the object appears to them. This appearance is mind-dependent sense-data. Physical objects are therefore not perceived directly. 

physical objects

Material objects, including things like tables, books, our own bodies, plants, mountains. 

primary quality

Properties that are ‘utterly inseparable’ from a physical object, whatever changes it goes through, even if it is divided into smaller and smaller pieces. The object has these properties ‘in and of itself’. Locke lists extension (he also talks of size), shape, motion, number, and solidity as primary qualities. 

secondary quality

Properties that physical objects have that are ‘nothing but powers to produce various sensations in us’. Locke lists ‘colours, sounds, tastes, and so on’, later adding smells and temperature.