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I know that the Battle of Hastings was in 1066 and that 2 + 2 = 4. But what, in philosophy, is knowledge?
Knowledge requires belief. One can only know that the Battle of Hastings was fought in 1066 if one believes that it was. But there is more to knowledge than belief. For one can believe a falsehood, whereas one cannot know a falsehood. John believes that Mary loves him, but cannot know that she loves him because she does not. And there is more to knowledge than believing a truth. Mary egoistically believes that everyone loves her, and infers that John loves her. And, completely coincidentally, he does. So Mary\'s belief that John loves her is true, but she does not know that he loves her.
What more than true belief is required for knowledge? Many philosophers have thought that the answer is justification. Mary\'s belief that John loves her is true, but unjustified. She does not have good reason to suppose that John loves her, but believes he does because she egoistically believes that everyone loves her. Knowledge, then, is true justified belief. I know that the Battle of Hastings was fought in 1066 because I believe that it was fought in that year, my belief is true, and I have good reason for my belief, perhaps because I read the information in a trustworthy history book.
The claim that knowledge is justified true belief was, however, refuted by Gettier. He showed that having a justified true belief is insufficient for knowledge. Suppose that Helen, one of my sisters, tells me that she is pregnant, on the grounds that her pregnancy test at the clinic was positive. I infer that one of my sisters is pregnant. I believe that one of my sisters is pregnant, and I have good reason to believe that one of my sisters is pregnant; my belief is justified. Further suppose that my belief is true, but not because Helen is pregnant. There was a mix up at the clinic and she is not pregnant, but my belief is true because, as a matter of complete coincidence, Christine, my other sister, is pregnant. My belief that one of my sisters is pregnant is true and justified. But I do not know that one of my sisters is pregnant. True justified belief is insufficient for knowledge.
What more than true justified belief is required for knowledge? One answer is this. A belief counts as knowledge only if it was acquired by a method that was, in the context, reliable. A method for acquiring beliefs is reliable just if it leads one to acquire beliefs which are true and does not lead one to acquire beliefs which are false. Trusting one\'s sensory experience is a reliable method for acquiring beliefs in most contexts. If one trusts one\'s sensory experience, one will acquire beliefs about the external world which are true; one will not acquire beliefs about the external world which are false (unless, say, one is on a hallucinogenic drug).
Trusting hospital pregnancy tests is also an example of what may seem, in most contexts, a reliable method for acquiring beliefs. But in the above example, the context of the mix-up at the hospital meant that it was not a reliable method. And this is why my true justified belief that one of my sisters is pregnant does not count as knowledge. For a belief counts as knowledge only if it was acquired by a method that was, in the context, reliable.
What, then, is knowledge? One answer is this: knowledge is true justified belief that was acquired by a method that was, in the context, reliable. A subject\'s belief counts as knowledge when they have good reason to have that belief, the belief is true, and it was acquired by a method that was, in the context, reliable. AJ
See also a priori and a posteriori; epistemology; scepticism.Further reading J. Dancy, An Introduction to Epistemology; , J. Foster, A.J. Ayer. |
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