Key Terms : Philosophy

Courtesy by edx :UQx: META101x Philosophy and Critical Thinking


the theory or study of knowledge, what constitutes knowledge, what distinguishes knowledge from belief or opinion, whether it is possible to have knowledge, and how knowledge can be understood through the methods of logic and argumentation (formal epistemology).

Three Kinds of Knowledge

Philosophers distinguish between three kinds of knowledge:

  • Knowledge by Acquaintance:

    This is the kind of knowledge we have of someone or something by direct acquaintance, when we say that Alex knows Dave or Veronique knows Paris like the back of her hand.

  • Know-How:

    We say that Dave knows how to ski. Know-how is a kind of skill or capacity to do something that is typically acquired through practice. Philosophers have wondered what the relationship is between know-how and know-that, and whether, for example, know-how always presupposes know-that or whether the two kinds of knowledge are independent of one another.

  • Know-Why:

    We can say that we know why something is the case or know what or where. The verb ‘to know’ takes wh-nominals. Some philosophers have argued that this shows that knowledge is very different from belief because the verb ‘to believe’ does take wh-nominals.

  • Propositional Knowledge or ‘Knowledge That’:

    Knowing-that or knowledge that some proposition is true or that some fact or state-of-affairs obtains is the kind of knowledge we are interested in exploring in this module.


Propositions are the bearers of truth-values – truth and falsity. Premises express propositions. The kind of knowledge that is involved in assessing an argument for soundness is, therefore, propositional knowledge.

A priori versus A posteriori Knowledge:

If a proposition can be known to be true independently of experience, experiment or observation, it is known a priori (prior to or independently of experience or observation). For example, ‘2+2=4’, ‘No cat is not a cat,’ and ‘It is either raining or it is not raining’ are propositions which can be known to be true without observation. If instead, a proposition can only be known on the basis of experience, experiment or observation, we say that it is known a posteriori (posterior to or after experience or observation). Whether, for example, we can know ‘My tea is currently 53 degrees Celsius,’ or ‘the Sun is 149.6 million kilometres from the Earth’ depends on observational evidence.

Scepticism (or Skepticism):

From the Greek term skepsis meaning investigation. The sceptic investigates the grounds for believing propositions and finding them doubtful, abstains from judging or believing altogether. That is, the sceptic neither believes nor disbelieves any proposition that cannot be established beyond doubt. Scepticism is to be distinguished from the ordinary incredulity we experience in regard to propositions which are doubtful but where the grounds for doubt can be removed. In its more radical forms, scepticism equates to universal doubt where assent is withheld from every proposition.


A theory or argument is circular if it presupposes the truth what it is required to establish or prove. No pun intended, circularity is a recurring problem in epistemology.

Dog chasing its tail


Certainty is attributed both to beliefs and to epistemic agents. We can say either that Harry is certain that 2+3=5 or that Harry’s belief is certain. Certainty thus marks a belief as meeting the highest epistemic standard. A belief is thus epistemically certain when it is not possible to doubt it. While a belief is psychologically certain when it is incorrigible (when someone can’t but believe it), a belief is said to be indubitable — beyond doubt or epistemically certain — even if no one is aware of its indubitability.


The fundamental categories of being or existence. Ontology is a branch of metaphysics. Metaphysicians are engaged in the task of working out what categories are needed for us to make sense of the world. For example, some metaphysicians include in their ontology categories like ‘substance’ and ‘attribute’ or ‘objects and properties’; some deny that the substance/attribute distinction is coherent. Some include ‘events’ as basic, irreducible entities; others attempt to reduce the category of events to those of objects and properties. Some ontologies include universals or common natures as real entities; others deny the existence of universals.


The view that all knowledge originates from the operation of our sensory or perceptual faculties. Empiricists deny that ideas are innate. At most that the capacity or faculty for acquiring ideas is part of the innate structure of the mind.


The view that all knowledge originates from the operations of reason or the intellect. Rationalists often endorse the idea that at least some of our ideas and the logical apparatus that we use to reason with are innate to the mind. Perception plays a secondary epistemic role: either that of triggering reason to produce knowledge or providing objects for belief and investigation by reason.


The view that knowledge attributions (e.g., ‘S knows that p’) exclude the possibility that p could be false.

In other words, if S knows that p, it is not possible for S to rationally doubt p. Knowledge entails epistemic certainty.


The view that knowledge attributions (e.g., ‘S knows that p’, where ‘S’ stands for the subject or person who knows and ‘p’ for the proposition known) do not exclude the possibility that p could be false. Fallible knowledge claims are sometimes referred to as ‘concessive knowledge attributions’ (CKA’s) – i.e., ‘S knows that p, but it is possible that q (where q entails not-p)’.

In other words, if S knows that p, it does not follow that S is epistemically certain that p.


The view that all talk of mental states and processes can be analysed in terms of human behaviour or dispositions to behave in certain predictable and observable ways.


Able to be thought about or conceived without incoherence, contradiction or absurdity.


A term that encompasses a range of subjective phenomena including sentience, experience, wakefulness, self-awareness, phenomenal experience where there is something that it is like to experience the world from the point of view of a subject.

Creature consciousness denotes the consciousness of whole organisms, in contrast with state consciousness, which is said of mental states. A state is intransitively conscious when the subject in that mental state is aware, and transitively conscious when the subject is aware or conscious of something, e.g., the approaching train.


Where two things are distinct by nature and so are able to be divided, a dualism holds between the two. Substance dualists hold that a person is composed of two distinct kinds of things or natures, mind and body. Property dualists or Epiphenomenalists hold that a person is a single, undivided entity which has, however, distinct kinds of properties: physical and mental.


The view that mental states should be analysed in terms of their functional roles (cognitive, conceptual and behavioural roles) in explaining the complex capacities of a system.

Identity Theory (Materialism):

The view that the mind is identical with the brain or central nervous system.

Multiple realisability:

A kind of mental state is said to be multiply realisable when it either does or could exist in different physical forms. Chairs, for example, are a multiply realisable kind because there are many different physical forms that chairs take (metal, wooden, plastic, etc). If a mental state like pain is multiply realisable, then different kinds of brain states and non-brain states could be pains.

Necessary and sufficient conditions:

If A is a necessary condition for B, then if A is not true, then B is not true. For example, ‘Steve is on the electoral role’ is necessary for the truth of ‘Steve votes.’ If A is a sufficient condition for B, then if A is true, then B is true. The truth of ‘Sam is a mouse’ is sufficient for the truth of ‘Sam is an animal’.

If A is sufficient for B, then B is necessary for A. Sam’s being an animal is necessary but not sufficient for Sam’s being a mouse. If A is necessary for B, then not-A is sufficient for not-B. Steve’s not being on the electoral role is sufficient for Steve’s not voting.

Non-reductive theories:

Deny the possibility of reducing talk about the mind and consciousness to the language of a more basic science.


Rules or standards of correctness that emerge from social interactions among individuals. Errors or mistakes arise when there is a failure to adhere to a norm.


The view that only physical events can cause other physical events and that the universe is, therefore, closed under a physical description.


Able to be or exist.


The view that the terms of our “folk psychology” can be exhaustively defined and explained in the terms of our best scientific theory — e.g., cognitive neuroscience.


The representational content or meaning of symbols or mental states — e.g., what a thought or mental state is about.


The formal or physical properties of symbols.

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