Michael Clark argues that the necessary and sufficient conditions for S knowing that p are:
(1) p is true,
(2) S believes that p,
(3) S is justified in believing that p, and
(4) S’s belief that p is fully grounded.
STEP 1: Clark observes that Gettier’s examples are stronger than they need to be since he presents cases in which an agent’s grounds for a belief deductively entail the proposition believed, whereas there may also be Gettier-type cases involving non-deductive grounds.
Example: Suppose that Smith forms the true belief that Jones owns a Ford based on the testimony of Brown, who is typically reliable, but who (on the present occasion) has mixed up Jones with someone else. Although Smith’s belief (based on Brown’s testimony) is true and justified, it fails to constitute knowledge because it rests on false grounds. Insofar as Brown’s testimony constitutes non-deductive grounds for believing that Jones owns a Ford, this is a Gettier-style example involving non-deductive grounds.
Upshots: (i) Insofar as Brown’s testimony constitutes non-deductive grounds for Smith’s belief, Gettier-style examples are effective within a non-deductive context. (ii) S knows that p only if her belief that p is not based on false grounds.
STEP 2: Clark argues that adding the fourth condition that an agent’s belief be based on true grounds is still insufficient for knowledge.
Example: Suppose that Smith forms the true belief that Jones owns a Ford based on the testimony of Brown, who is typically reliable, but who (on the present occasion) is simply making up a claim that (unknown to Brown) happens to be true. Although Smith’s belief is true, justified, and rests on true grounds (i.e., Brown’s claim that Jones owns a Ford), it still fails to constitute knowledge. Thus, we have a Gettier-style example involving true grounds.
Upshot: Although Smith’s belief is based on true grounds, Smith lacks knowledge because the grounds on which he accepts these true grounds, viz. that Brown knows them, are false.
STEP 3: Clark claims that if we keep inquiring about someone’s grounds for accepting certain grounds, and the grounds for accepting those grounds, and so on, we eventually come to a place where it would be inappropriate to ask for further grounds.
Example: A series of questions posed to Smith about why he believes Jones owns a Ford will eventually culminate in an answer, which we would deem out of order to question further.
Upshot: There is always some finite list of grounds that can be offered for a belief.
STEP 4: Clark posits that if one of the grounds in the chain of supporting grounds for a certain belief is false, then that belief fails to constitute knowledge.
Example: If any of the beliefs in the chain of Smith’s grounds for believing Jones owns a Ford are false, we may deny that Smith has knowledge. If all the beliefs in the chain are true, then Smith’s belief that Jones owns a Ford is fully grounded.
Upshot: Being fully grounded is a necessary condition for a belief to constitute knowledge.
Clark concludes that if we add the requirement that S’s belief that p be fully grounded to the requirement that p be true, S believe that p, and S’s belief that p be justified, we arrive at conditions that are jointly sufficient for knowledge.
1. Is Clark’s analysis of knowledge a successful response to Gettier-style counterexamples? If not, can you recommend any changes that would improve Clark's account?