1. Nozick’s Analysis of Knowledge
Nozick is responding to Gettier’s claim that the traditional tripartite definition of knowledge as justified true belief is inadequate. Nozick’s analysis is specified by the following four conditions, which together are necessary and sufficient for knowledge:
3. ¬ (1) → ¬ (2)
4. (1) → (2).
The symbol → is non-standard: Nozick uses it for his relation of subjunctive conditionality. A → B means that if A were the case, then B would also B the case. This differs from logical implication ⊃. If it is true that A ⊃ B, then in all possible worlds in which A is true, so is B. Nozick uses A → B to mean the much more restricted case in which in the closest group of possible worlds in which A is the case, so is B. We are also using the following symbols: p is a proposition, a is a subject, B is the relation of belief so that Bap means that a believes p; ¬ is negation and → is Nozick’s subjunctive conditional.
Dancy gives an illustration for which he cites Lewis of this crucial distinction. Lewis considers the conditional ‘if kangaroos had no tails, they would topple over’. This is a good illustration of A → B and not of A ⊃ B. In some possible worlds, the Australian tourist board gives the kangaroos crutches. This group of possible worlds is certainly more remote than the nearest possible world in which kangaroos have no tails and are unstable. So A → B is true but A ⊃ B is false because A does not entail B.
One of the terms for this analysis is ‘truth-tracking’ because the subject’s belief is co-variant with the truth of p; if it were the case that p then the subject would believe it and if it were not the case that p then a would not believe it. It has also been known as a counter-factual analysis because of the way in which it discusses near possible worlds distinct to the actual world in order to assess knowledge claims in the actual world.
Nozick introduces his two new conditions (3) and (4) in order to handle cases which had not been soluble on the previous bases. Gettier cases involve erroneously scoped referencing in which the subject appears to have a justification for believing p and p is true and yet the situations appear to fall short of knowledge. For example: “Two other people are in my office and I am justified on the basis of much evidence in believing the first owns a Ford car; though he (now) does not, the second person (a stranger to me) owns one. I believe truly and justifiably that someone (or other) in my office owns a Ford car, but I do not know someone does.” Condition (3) eliminates this type of case as an instance of knowledge, which is a point in favor of Nozick’s analysis.
Nozick’s introduction of condition (4) occurs in the context of a skeptical scenario termed ‘Brain in a Vat’ (“BIV”) by Putnam. The subject is in fact a disembodied brain being stimulated by electrochemical means to have experiences; these being in the base case scenario all of the same experiences as in the current world. This skeptical hypothesis will produce important implications for Nozick’s analysis, to be discussed in the next section. The power of the hypothesis lies in the fact that while it is doxically identical to the actual world, almost everything believed in it is false.
As Nozick points out, his subjunctive analysis is related to but more restricted than the prior causal analysis. Under BIV, the subject can be brought to believe that BIV is true by being given appropriate stimulation. There is a good causal link between the event and the belief formation, but this cannot count as knowledge because it is fortuitous. Nozick can exclude this type of counterexample because it fails condition (4): in the close world to that of the BIV subject where he is not given the relevant stimulation, he no longer believes BIV although it is still true.
1.3. Skeptical Implications and Non-Closure
There is a major ‘heavyweight implication’ of Nozick’s analysis that is highly counter-intuitive. It will be instructive to see how he resolves it. The following principle, termed the closure principle, seems valid:
(CP): Kap & Ka(p -∃ q) → Kq.
The symbol -∃ is used to signify entailment, and so CP may be expressed as ‘if it were the case both that a knows that p and a knows that p entails q, then it would be the case that a knows q’; K is the two-place relation of belief used similar to B for belief previously.
This seems entirely plausible but Nozick uses BIV to argue that it is false. Let p be any everyday proposition such as ‘a is in London’. Let q be the negation of BIV. It is clear that p entails q, that a knows this entailment and that p is true and so under CP, a knows that BIV is false. Yet this is exactly the skeptical scenario that appears difficult to defeat.
Nozick’s dramatic response to this is to deny CP: “Knowledge is not closed under known logical implication”. He explains this by deriving it from the non-closure of (3): “That you were born in a certain city entails that you were born on earth. Yet contemplating what (actually) would be the situation if you were not born in that city is very different from contemplating what situation would hold if you weren’t born on earth.”
Nozick introduces a further refinement to handle what he terms the grandmother case. A grandmother comes to know that her grandson is healthy by seeing him. Were he not however, she would nevertheless be told that he was, in order to spare her distress. Nozick wishes to preserve this as a case of knowledge even though it fails condition (3).
This he does by adding the requirement ‘via method M’ to (2), (3) and (4). For a case to represent knowledge, M must not change in the relevant possible counter-factual situations. This means that the grandmother has knowledge in all the possible worlds in which she learns her grandson is healthy by seeing him, and does not in the possible worlds in which she relies on inaccurate testimony. This appears to be the correct result.
2. Objections to Nozick
Forbes defends CP by putting pressure on Nozick’s line that the same method M must be used in (2), (3) and (4) in order to avoid incorrect knowledge ascriptions in the grandmother case. Forbes points out that M being reliable in the actual world where p is true does not entail that M is reliable in even the closest possible worlds where p is false.
The example given is of a reliable computer that can also check its own status. The proposition p is that the computer is functioning normally. The question is whether a subject can acquire knowledge that p by asking the computer to report its own status. If p, then this method M is reliable. However, if not p, then method M is by hypothesis no longer reliable. Thus there is no way to hold M constant while varying the truth value of p in order to assess whether the belief of the subject is co-variant with p.
Forbes allows that Nozick may have a response along lines similar to those used in an example that Nozick himself gives. This is of a vase in a box that is pressing a switch. The switch activates a holographic projector set to show a vase in the box. An observer passes all of (1) – (4) in respect of p, there is a vase in the box, and yet this is not a knowledge case. But Forbes holds that Nozick would then need to concede that the counter-factual analysis was inappropriate for all inferences and this would be arbitrary and severe for Nozick’s analysis. Perhaps Nozick here can instead adopt in some form Harman’s suggestion that all the lemmas be true.
Wright also attacks Nozick’s claim to have defeated the sceptical argument by introducing non-closure. He notes that using Nozick’s standard p and q (p = ‘I have a hand’; q = ¬ BIV) produces a problem for the ¬q scenario. Here, BIV is true and so p is false. We can assume that BIV is one of the relevant ¬p scenarios to be considered in assessing whether Kap. But if so, then subject a fails condition (3) because, even though p is false, Bap.
So Wright argues that Nozick must assume that BIV is not one of the relevant ¬p scenarios. And he further uses Nozick’s own argumentation against him with the following line, in which (I) represents ‘had it not been the case that I have a hand, then it would still not have been the case that BIV’.
(I): ¬p → q
(II): ¬q → ¬p
(III): ¬q → q
(II) is simply the statement that in BIV, I do not have a hand and then the reductio (III) follows by modus ponens from (I) and (II). As Wright points out, this could be seen as a refutation of the skeptic, but that line is not open to Nozick who wishes to agree that BIV is logically possible.
Wright allows Nozick the response of denying that transitivity holds for counter-factual conditionals. This would break the step to (III).
Garrett defends Nozick against a purported counterexample given by Martin. Martin’s example considers a subject a placing a bet that pays if either of two horses wins. Subject a uses the unreliable method of finding out whether his horse won in the first race of simply cashing in his slip after the second race while avoiding any information about the first race. If his slip pays, he assumes that the first horse won whereas in fact it could have been the horse in the second race.
Assume that the first horse did in fact win, and this is proposition p. The horse in the second race did not win. Condition (3) seems satisfied because ¬p → ¬Bap. Also, (4) seems satisfied. And yet this surely cannot be a case of knowledge because of the good fortune of a that the second horse did not win; a has failed to consider a relevant alternative.
Nozick’s response will be that in fact the possible worlds in which the first horse loses and the second wins are close enough that they have to be included in the assessment of whether Kap, whereas some possible worlds do not, such as one in which the betting machine has malfunctioned and is paying all slips. And then it is precisely the failure of Kap to track p in those close worlds that means (3) is not satisfied and this is not a knowledge case.
But Garrett has a refined version of this counterexample that he thinks is more dangerous to Nozick. Proposition q is that the father of person A is a philosopher; q is true. Proposition p is that the father of person B is a philosopher. Subject a uses the unreliable method M of forming Bap if a understands that q. It transpires unbeknownst to a that A and B are brothers, so in fact p. This fulfills conditions (1) – (4) but cannot be knowledge because it relied on the random unknown fact of A and B being brothers.
2.4. Gordon’s Response to Garrett
Gordon replies to Garrett’s objection by narrowing the scope of the problem of the father of A being a philosopher. Gordon notes that Nozick can appeal to his insistence that method M be held constant across the counter-factual scenarios. If method M means that a can legitimately infer facts about the father of A from knowing facts about the father of B and knowing that A and B are brothers, then M is reliable. It only becomes unreliable if extended to the general unrelated population. So can Nozick argue that this is in fact no longer M? For Garrett, the question becomes “why is it a requirement of knowledge that one have good grounds for thinking one’s method reliable?”
Gordon holds that Nozick has in fact replaced the tripartite analysis of knowledge as justified true belief (“JTB”) with his four conditions. Nozick is not therefore committed to JTB, and “even if Garrett can show a case in which one can meet Nozick’s conditions while using an unreliable method, he won’t have arrived at a clear counterexample to Nozick”.
2.5. Garrett’s Rejoinder to Gordon
Garrett responds by insisting “it is no presupposition of my counterexamples that it is necessary for knowledge that one have good grounds for thinking one’s method reliable if it is reliable”. Garrett agrees that if his counterexample shows unjustified true beliefs that meet all of Nozick’s conditions, and if JTB is required for knowledge, then he has found cases where Nozick ascribes knowledge incorrectly. However Garrett further claims that his counterexamples are valid against Nozick whether or not JTB is required. This seems strange however.
Garrett seeks to draw an analogy with the standard Gettier cases, saying that it is possible to explain why his father of A case is a counterexample to Nozick by showing the presence of unjustified true beliefs without insisting that justification is essential to knowledge. The idea seems to be that there is no entailment here. This seems true, but Garrett does not specify what alternate method he has to show that Nozick has falsely ascribed knowledge. Or alternatively Garrett may be thinking of a negative condition. Lack of justification is sufficient to disprove a knowledge claim, while the presence of justification is insufficient to prove a knowledge claim. This separation seems somewhat arbitrary though. In summary, Gordon’s defense of Nozick appears successful.