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 | |  Closure Fails on a Relevant Alternatives Approach | |
The second version of the argument from the analysis of knowledge has it that any relevant alternatives view, not just tracking accounts, is in tension with K. An analysis is a relevant alternatives account when it meets two conditions. First, it yields an appropriate understanding of ‘relevant alternative.’ Dretske's approach qualifies since it allows us to say that an alternative A top is relevant if and only if: - اقتباس :
- CRA: were p false, A might hold.
According to the second condition, the analysis must say that knowing p requires ruling out allrelevant alternatives to p but not all alternatives to p. Dretske's approach qualifies once again. It says an alternative A is ruled out on the basis of R if and only if the following condition is met: - اقتباس :
- CRR: were A to hold R would not hold.
And, on Dretske's approach, an alternative A must be ruled out if and only if A meets CRA.So the tracking account is a relevant alternatives approach. But why say that relevant alternatives accounts of knowledge are in tension with K? We will say this if, like Dretske, we accept the following crucial tenet: the negation of a proposition p is automatically a relevant alternative to p(no matter how bizarre or remote not-p might be) but often not a relevant alternative to things that imply p. For a relevant alternatives theorist, this tenet suggests that we can know something ponly if we can rule out not-p but we can know things that entail p even if we cannot rule out not-p, which opens up the possibility that there are cases that violate K. For while our inability to rule out not-p stops us from knowing p it does not stop us from knowing things that entail p. And an example is ready to hand: the zebra case. Perhaps you cannot rule out mule; but that stops you from knowing not-mule without stopping you from knowing zeb. These points can be restated in terms of the conclusive reasons account. For Dretske, the negation of a proposition p is automatically a relevant alternative since condition CRA is automatically met; that is, it is vacuously true that: - اقتباس :
- were p false, not-p might hold.
Therefore mule is a relevant alternative to not-mule. Furthermore, you fail to know not-mulesince you cannot rule out mule: you believe not-mule on the basis of your zebra-in-the-cage percepts, but you would still have these if mule held, contrary to CRR. Yet you know zeb in spite of your inability to rule out mule, for were zeb false you would not have your zebra-in-the-cage percepts.According to the second version of the argument from the analysis of knowledge any relevant alternatives view is in tension with K. How compelling is this argument? As Dretske acknowledged (2003), it is actually a weak challenge to K since some relevant alternatives accounts are fully consistent with K. For an example, we have only to adapt the safe indication view so as to make it clear that it is a relevant alternatives account (Luper 1984, 1987c, 2006).The safe indication view can be adapted in two steps. First, we say that an alternative to p, A, is relevant if and only if the following condition is met: - اقتباس :
- SRA: In S's circumstances, A might hold.
Thus any possibility that is remote is automatically irrelevant, failing SRA. Second, we say that Ais ruled out on the basis of R if and only if the following condition is met: - اقتباس :
- SIR: were R to hold A would not hold.
This way of understanding relevant alternatives upholds K. The key point is that if S knows p on the basis of R, and is thus able to rule out p's relevant alternatives, then S can also rule out q's relevant alternatives, where q is anything p implies. If R were to hold, q's alternatives would not.Apparently, the relevant alternatives account can be construed in a way that supports K as well as a way that does not. Hence Dretske is not well positioned to claim that the relevant alternatives view leads “naturally” to closure failure. 2.3 Closure and ReliabilismOn one version of reliabilism (defended by Ramsey 1931 and Armstrong 1973, among others) one knows p if and only if one arrives at (or sustains) the belief p via a reliable method. Is the reliabilist committed to K? The answer depends on precisely how the relevant notion of reliability is understood. If we understand reliability as tracking theorists do, we will reject closure. But there are other versions of reliabilism which sustain K. For example, the safe indication account is a type of reliabilism. Also, we could say that a true belief p is reliably formed if and only if based on an event that usually would occur only if p (or a p-type belief) were true. Any event that, in this sense, reliably indicates that p is true will also reliably indicate that p's consequences are true.3. The Argument From Nonclosure of Knowledge ModesDretske argued (2003, 2005) that we should expect K failure because none of the modes of gaining, preserving or extending knowledge are individually closed. Dretske made his point in the form of a rhetorical question: “how is one supposed to get closure on something when every way of getting, extending and preserving it is open (2003: 113–4)?” 3.1 Knowledge Modes and NonclosureAs examples of modes of gaining, sustaining and extending knowledge Dretske suggested perception, testimony, proof, memory, indication, and information. To say of these items that they are not individually closed is to say that the following modes closure principles, with or without the parenthetical qualifications, are false: - اقتباس :
- PC: If S perceives p, and (S believes q because S knows) p entails q, then S perceives q.
TC: If S has received testimony that p, and (S believes q because S knows) p entails q, thenS has received testimony that q.
OC: If S has proven p, and (S believes q because S knows) p entails q, then S has proven q.
RC: If S remembers p, and (S believes q because S knows) p entails q, then S remembers q.
IC: If R indicates p, and (S believes q because S knows) p entails q, then R indicates q.
NC: If R carries the information p, and (S believes q because S knows) p entails q, then Rcarries the information q. And, according to Dretske, each of these principles fails. We may perceive that we have hands, for example, without perceiving that there are physical things. 3.2 Responses to DretskeThere have been various rejoinders to Dretske's argument from nonclosure of knowledge modes.First, failure of one or more of the modes closure principles does not imply that K fails. What matters is whether the various modes of knowledge Dretske discusses position us to know the consequences of the things we know. In other words, the issue is whether the following principle is true: - اقتباس :
- T: If, while knowing p via perception, testimony, proof, memory, or something that indicates or carries the information that p, S believes q because p entails q, then S knows q.
Second, theorists have defended some of these modes closure principles, such as PC, IC and NC. Dretske rejects these three principles because he thinks perception, indication and information are best analyzed in terms of conclusive reasons, which undermines closure. But the three principles (or something very much like them) may be defended if we analyze perception, indication and information in terms of safe indication. Consider IC and NC. Both are true if we analyze indication and information as follows: - اقتباس :
- R indicates p iff p would be true if R held.
R carries the information that p iff p would be true if R held. A version of PC may be defended if we make use of Dretske's own notion of indirect perception (1969). Consider a scientist who studies the behavior of electrons by watching bubbles they leave behind in a cloud chamber. The electrons themselves are invisible, but the scientist can perceivethat the (invisible) electrons are moving in certain ways by perceiving that the (visible) bubbles left behind are arranging themselves in specific ways. What we directly perceive positions us to perceive various things indirectly. Now assume that when we directly or indirectly perceive p, and this causes us to believe q, where p entails q, we are positioned to perceive q indirectly. Then we are well on our way to accepting some version of PC, such as, for example: - اقتباس :
- SPC: If S perceives p, and this causes S to believe q, then S perc
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