Bin Zhao

The two-visual-systems hypothesis proposed by Goodale and Milner is a radical one. If it were to be true, then our common sense such as we are acting on what we are perceiving should be completely abandoned. In this paper, I argue that the hypothesis over-generalizes what happens in simple tasks to what happens in complex tasks. By contrast, I demonstrate that what happens in complex tasks is compatible with our common sense. In a word, though what we are acting on may come apart from what we are perceiving in some cases, that is not the whole story.

According to the sensitivity account of knowledge, S knows that p only if S's belief in p is sensitive in the sense that S would not believe that p if p were false. It is widely accepted that the sensitivity condition should be relativized to belief-formation methods to avoid putative counterexamples. A remaining issue for the account is how belief-formation methods should be individuated. In this paper, I argue that while a coarse-grained individuation is still susceptible to counterexamples, a fine-grained individuation makes the target belief trivially insensitive. Therefore, there is no principled way of individuating belief-formation methods that helps the sensitivity account to accommodate different cases.

The sensitivity account of knowledge is a modal epistemology, according to which S knows that p only if S's belief in p is sensitive in the sense that S would not believe that p if p were false. There are different ways to state the sensitivity condition by means of a possible worlds heuristic. The sensitivity account is thus rendered into different versions. This paper examines cases of knowledge and cases of luckily true beliefs (e.g., the Gettier cases) and argues that no version of the sensitivity account accommodates all cases. Therefore, the account is unsuccessful as an account of knowledge.

Depending on whether we are somewhat tolerant of nearby error-possibilities or not, the safety condition on knowledge is open to a strong reading and a weak reading. In this paper, it is argued that induction and conjunction introduction constitute two horns of a dilemma for the safety account of knowledge. If we opt for the strong reading, then the safety account fails to account for inductive knowledge. In contrast, if we opt for the weak reading, then the safety account fails to accommodate knowledge obtained via the method of conjunction introduction.

Modal epistemologies aim to explicate the necessary link between belief and truth that constitutes knowledge. This strain of epistemological theorizing is typically externalist; hence, it does not require that the agent know or understand the nature of the knowledge-constituting link. A central concern of modal epistemology is to articulate conditions on knowing such that no merely lucky true belief counts as knowledge. In the effort to eliminate luck, epistemic principles are often cast modally, requiring that an agent’s belief is true not only in the actual world but also in relevant possible worlds, indicating that the link between truth and belief is more than an actual world lucky coincidence. (Note, then, that this entry is not about the epistemology of modals—statements involving modal operators such as “necessarily,” “possibly,” and the like—but about the use of modal principles in characterizing the nature of knowledge in general. For purposes of disambiguation and in deference to the other topic, perhaps “modalized epistemologies” would be a better term, though it is not typically used here.) Modal epistemologies typically have antiskeptical consequences, but the strengths of the antiskeptical results vary significantly, especially between the two best-known modal principles, sensitivity and safety.

According to the sensitivity account of knowledge, S knows that p only if S’s belief in p is sensitive in the sense that S would not believe that p if p were false. The sensitivity condition is usually relativized to belief-formation methods to avoid putative counterexamples. A remaining issue for the account is where methods should be mentioned in the sensitivity subjunctives. In this paper, I argue that if methods are mentioned in the antecedent, then the account is too strong to accommodate inductive knowledge; if methods are mentioned in the consequent, then the account is too weak to eliminate some luckily true beliefs from the realm of knowledge. Therefore, the strategy to relativize the sensitivity condition is undermined by inductive knowledge and some luckily true beliefs.

It has been argued that an advantage of the safety account over the sensitivity account is that the safety account preserves epistemic closure, while the sensitivity account implies epistemic closure failure. However, the argument fails to take the method-relativity of the modal conditions on knowledge, viz., sensitivity and safety, into account. In this paper, I argue that the sensitivity account and the safety account are on a par with respect to epistemic closure once the method-relativity of the modal conditions is taken into account. Therefore, epistemic closure is no longer an arbiter in the debate.

According to the safety account of knowledge, one knows that p only if one's belief could not easily have been false. An important issue for the account is whether we should only examine the belief in the target proposition when evaluating whether a belief is safe or not. In this paper, it is argued that if we only examine the belief in the target proposition, then the account fails to account for why beliefs in necessary truths could fall short of knowledge. But, if we also examine beliefs in other relevant propositions, then the account fails to preserve epistemic closure. Therefore, the safety account cannot find a safe path between epistemic closure and necessary truths.

According to the safety account of knowledge, one knows that p only if one’s belief could not easily have been false. An important issue for the account is whether we should only examine the target belief when evaluating whether a belief is safe or not. In this paper, it is argued that, if we should only examine the target belief, then the account fails to account for ignorance of necessary truths. But, if we should also examine beliefs in other relevant propositions, then the account fails to account for knowledge from falsehood. Therefore, the safety account of knowledge is undermined by knowledge from falsehood and ignorance of necessary truths.

The safety condition is supposed to be a necessary condition on knowledge which helps to eliminate epistemic luck. It has been argued that the condition should be globalized to a set of propositions rather than the target proposition believed to account for why not all beliefs in necessary truths are safe. A remaining issue is which propositions are relevant when evaluating whether the target belief is safe or not. In the literature, solutions have been proposed to determine the relevance of propositions. This paper examines a case of luckily true belief—thus a case of ignorance—and a case of knowledge. It argues that no solution in the literature offers a correct verdict in either case. Therefore, the strategy to globalize safety remains unsatisfactory.