What is Knowledge? • A large part of philosophy involves coming up with deﬁnitions. • A deﬁnition of knowledge was ﬁrst offered by Plato in the Theaetetus. • Plato’s account provided what he thought were the necessary and sufﬁcient conditions for knowledge.
Necessary and Sufﬁcient Conditions Deﬁnitions in philosophy are often offered in terms of necessary and sufﬁcientconditions. A necessary condition is something that must hold in order for something to bethe case. E.g. It is a necessary condition of being a human that you are a mammal, but this is not sufﬁcient. A sufﬁcient condition is something that assures that something is the case. E.g. It is a sufﬁcient condition for being a mammal that you are a human, yet it is not necessary. It is usual for deﬁnitions to be stated in terms of individually necessary andjointly sufﬁcient conditions. E.g. A necessary condition for being a sister is that you are female. However,thisaloneisnotsufﬁcientforsisterhood;itisalsonecessary that you be a sibling. As such there are two individually necessary conditionsforbeingasisterandthesearejointlysufﬁcient.Therefore, we can deﬁne a sister as a female sibling.
What is knowledge? • There are generally thought to be 3 individually necessary and jointly sufﬁcient conditions for something to count as knowledge. 1. Belief condition: in order for (x) to know (p), (x) must believe that (p). 2. Truth condition: in order for (x) to know (p), (p) must be true. 3. Justiﬁcation condition: in order for (x) to know (p), (x)’s true belief that (p) must be justiﬁed in some way. • As such, we can deﬁne knowledge as justiﬁed true belief (JTB); thus, if one has a knowledge one has a JTB, and if one has a JTB one has knowledge.
What is knowledge? The Gettier Problem Jennifer believes that Brad is having an affair with Angelina and, in fact, it’s true that Brad and Angelina are having an affair. Jennifer’s suspicions were aroused by the fact that the paparazzi photographed the pair together in a restaurant on a night when Brad had said that he was busy ﬁlming. As such, Jennifer’s belief is justiﬁed. However, what Jennifer doesn’t know is that Angelina was actually out with a Brad impersonator that night (Brad was actually ﬁlming and Angelina was so besotted that she hired a look- alike). So Jennifer has a justiﬁed true belief that Brad and Angelina are having an affair, but does she have knowledge? Does Jennifer know about Brangelina? • Examples like this (Gettier-style counterexamples), which problematize the tripartite deﬁnition of knowledge as JTB, have been common since Edmund Gettier’s hugely inﬂuential 1963 paper ‘Is knowledge justiﬁed true belief?’.
What can we know? René Descartes 1596-1650 Father of Modern Philosophy Cogito ergo sum
What can we know? Background to Descartes • Medieval hierarchy of knowledge 1. Revelation 2. Authority 3. Reason 4. Observation • The Scientiﬁc Revolution The new science of Copernicus, Galileo, etc. contradicted some of the central claims of Christianity (geocentricism, etc.). As such, there is an intellectual crisis prompting some sceptics to claim that knowledge is impossible.
What can we know? Meditations on First Philosophy (1641) Descartes’ Aim: ‘to demolish everything completely and start right again from the foundations.’ Descartes’ Method 1. Hyperbolic (Cartesian) doubt Descartes’ ‘method of doubt’ entails that if anything can be doubted, however slightly, then we are to treat it as if it is manifestly false and reject it outright. 2. Foundationalism Descartes will not subject each and every one of our opinions to this hyperbolic (exaggerated) doubt, as this would be a Sisyphean task. Rather, Descartes aims to test the ‘foundations’ of what we claim to know - ‘as the removal from below of the foundation necessarily involves the downfall of the whole ediﬁce’. Descartes identiﬁes the ﬁrst potential foundation for knowledge as experience derived from the senses.
What can we know? Dream Hypothesis (Meditation I) ‘There are no certain signs by which we may clearly distinguish wakefulness from sleep.’ – The fact that I cannot be certain that I am not now dreaming gives us reason to doubt the reliability of the senses. – If something can be doubted then it ought to be treated as if manifestly false. – This entails that all claims that are grounded on the reliability of the senses are open to doubt. – The entire class of beliefs that depend upon the senses must, therefore, be treated as if manifestly false. Having dispensed with experience, Descartes next turns his mind to an alternate foundation for knowledge - reason: – ‘for whether I am awake or dreaming, it remains true that two and three make ﬁve, and that a square has but four sides’.
What can we know? Demon Hypothesis (Meditation I) ‘I will suppose… that some malignant demon, who is at once exceedingly potent and deceitful, has employed all his artiﬁce to deceive me.’ – In this way, Descartes puts pay to the realm of that gained through reason in like manner to that derived from sense experience. – In case you ﬁnd the introduction of a malevolent genie too much to bear, Hilary Putnam (Reason, Truth, and History, 1981) updates the argument by asking you to consider the possibility you are a brain in a vat and that your experiences are just electronic signals being sent to your disembodied brain by an evil scientist. This thought experiment also forms the plot of the Hollywood blockbuster The Matrix.
What can we know? The Cogito At the outset of Meditation II Descartes states that: ‘The Meditation of yesterday has ﬁlled my mind with so many doubts, that it is no longer in my power to forget them... I suppose, accordingly, that all the things which I see are false (ﬁctitious); I believe that none of those objects which my fallacious memory represents ever existed; I suppose that I possess no senses; I believe that body, ﬁgure, extension, motion, and place are merely ﬁctions of my mind. What is there, then, that can be esteemed true? Perhaps this only, that there is absolutely nothing certain.’ In order to progress, he must establish one thing that is certain and indubitable. This eventually leads him to the cogito: ‘this proposition I am, I exist, is necessarily true each time it is expressed by me, or conceived in my mind.’ The cogito delivers subjective certainty; I can be sure of how things seem to me. The challenge for Descartes and his successors is how, if at all, we can move from subjective to objective knowledge of the world.
How can we know? Rationalism • Descartes is a Rationalist. Rationalists believe that knowledge can be acquired by reason alone, without recourse to experience. Such knowledge, it is claimed, must somehow be present in the mind at birth (innatism). – In fact Descartes depends upon an innate idea of God (the trademark argument) in attempting to escape the demon hypothesis. • Knowledge which is known via reason alone is called a priori. – E.g.1. ‘2+2=4’ • Analytic propositions, which are made true (or false) by the meanings of their terms alone, are known a priori. – E.g.2. ‘All brothers are male’ • All a priori truths are necessary - they could not possibly be false; they must be true. – E.g.3. ‘Either Jim is in Edinburgh or he is not’
How can we know? Empiricism • In opposition to Rationalists like Descartes are the Empiricists; for example, John Locke (1632-1704) and David Hume (1711-1776). Empiricists believe that knowledge depends upon experience derived from the senses. As such, the mind is a ‘tabula rasa’ at birth; innatism is false. • Knowledge which is derived from sense experience is called a posteriori. – E.g.4. ‘There are four men in the classroom’ • Such propositions are said to be synthetic as they are not true (or false) due to the meaning of their terms alone (they synthesise different concepts). – E.g.5. ‘Jim has a brother’ • All a posteriori claims are contingent - even if true, they might possibly have been false. – E.g.6. ‘Jim is in Edinburgh’
How do we know what we know? • Rationalism • Empiricism – A priori knowledge – A posteriori knowledge – Analytic – Synthetic – Necessary – Contingent The problem, an empiricist will claim, is that whilst a priori/analytic knowledge delivers certainty, it is actually rathertrivial and worthless. The knowledge that we actually wantabout the world is of the a posteriori/ synthetic type.However, the Rationalist will respond, this ‘knowledge’ is farfrom certain.
Details James Mooney Open Studies The University of Edinburgh email@example.com www.ﬁlmandphilosophy.com @ﬁlm_philosophy