Propositional and doxastic justification

Drawing on the results of previous chapters, the proposal is made to interpret the complex operator ⌜¬K¬K⌝ as encoding propositional justification and the complex operator ⌜¬K¬K⌝ as encoding doxastic justification—where in each case justification is understood to be justification all things considered. Accordingly, not only propositional but also doxastic justification is construed as a feature of one’s epistemic situation rather than a feature of one’s beliefs. On this view, both types of justification are non-factive. The proposed account is defended against a number of putative counterexamples, the allegation that it confuses epistemic permissibility with epistemic blamelessness, and the charge that it fails to heed plausible reliabilist constraints on justification. At crucial junctures this defence relies on the availability of theorems governing the aforementioned complex operators that were proved in chapter 5.

Competing views

The present account, which construes justification as a kind of epistemic possibility of knowing, or of being in a position to know, competes with three recently advanced theories of justification. Of these competitors, the first two construe doxastic justification as the metaphysical possibility of knowing. While they differ in some details, these views share certain problematic features: they fail to yield a corresponding account of propositional justification, have trouble vindicating an intuitive principle of closure for justified belief, and fail to comply with the independently plausible principle that if one has a justified belief, one is in no position to rule out that one has knowledge. The present account does not have these problematic features. According to the third competitor, |φ‎| is propositionally justified in one’s situation just in case it would be abnormal—and so require explanation—if |φ‎| were to be false in the presence of the evidence that one possesses in that situation. This normic theory of justification validates the principle that propositional justification agglomerates over conjunction, and in so doing, violates the constraint that propositions of the form ⌜φ‎ & ¬Kφ‎⌝ never be justified. It likewise contradicts the independently plausible principle that whenever |φ‎| is propositionally justified all things considered, |¬Kφ‎| is not. The present account does not face these problems, since it rejects the relevant agglomeration principle and treats the condition encoded by ⌜¬K¬Kφ‎⌝ as luminous.

Concluding Remarks

According to the account of epistemic justification developed in this book, one has propositional justification for p just in case one is in no position to know that one is in no position to know p; and one has doxastic justification for p just in case one is in no position to know that one does not know p. The account gives internalists much of what they want from a theory of justification—in particular, a notion of justification according to which propositional justification is non-factive and luminous, underwrites principles of positive and negative introspection, and remains available to the victims of systematic deception. All the while, that notion is explained in terms of other notions that clearly belong to the knowledge-firsters’ toolkit, and coheres with an externalist account of the grounds for justification.

Grounds for justification

We must distinguish between the condition of a proposition’s being justified in one’s situation and the metaphysical grounds determining that this condition obtains. While the former is luminous, the latter need not be. It is argued that knowing is a strict full ground for doxastic justification, and being in a position to know is a strict full ground for propositional justification. It follows that facts about one’s evidence that serve as strict partial grounds for knowing are strict partial grounds for doxastic justification, and facts about one’s evidence that serve as strict partial grounds for being in a position to know are strict partial grounds for propositional justification. Even if only partial, such evidential grounds can only be assumed to be available in some, but not all, cases in which one has doxastic justification without knowing, and propositional justification without being in a position to know. A more comprehensive account identifies facts about evidential probabilities as facts that yield strict full grounds for justification. While one’s evidence is the totality of what one is in a position to know, the evidential probability of p equals the probability of p conditional on one’s evidence. The account requires taking the notion of evidential probability as primitive. It uniformly applies to all cases of justification, including the bad cases envisaged by radical scepticism. Degrees of strength of justification are explained in terms of facts about evidential probabilities. Just as their grounds, degrees of strength of justification are not luminous, even if justification is.

Outline of a theory of justification

Core theses of the novel account of justification to be developed are first stated: one has propositional justification for p just in case one is in no position to know that one is in no position to know p; and one has doxastic justification for p just in case one is in no position to know that one does not know p. Unlike other theories that conceive of justification in terms of the metaphysical possibility of knowing, the present account thus construes it as a distinctive kind of epistemic possibility. It treats propositional justification as non-factive, both its presence and its absence as luminous conditions, and by assuming a weak non-normal modal logic for knowledge and being in a position to know, validates principles of positive and negative introspection for it. The account thereby attributes features to justification that internalists care about. But it does so without construing justification as an internal condition. The account allows one to systematically distinguish between the condition of being justified and the metaphysical grounds for its obtaining, thereby heeding externalist insights into the difference between the good cases and the bad cases envisaged by radical scepticism. Lines of argument that show the account’s potential, e.g. in dealing with the preface and lottery paradoxes, are previewed, and so are lines of defence against challenges and objections, including prominent anti-luminosity arguments.

On sharp and single-conclusion justification models

Justification awareness models (JAMs) were proposed by S. Artemov as a tool for modelling epistemic scenarios such as Russell’s prime minister example. It was demonstrated that the sharpness and the single-conclusion property of a model play an essential role in the epistemic usage of JAMs. The problem to axiomatize these properties using the propositional justification language was left opened. We propose the solution and define a decidable justification logic $\textsf{J}_{\textit{ref}}$ that is sound and complete with respect to the class of all sharp single-conclusion justification models. We also provide the complete axiomatizations for the classes of all single-conclusion justification models and all sharp justification models.

On the Relationship between Propositional and Doxastic Justification

I argue against the orthodox view of the relationship between propositional and doxastic justification. The view under criticism is: if p is propositionally justified for S in virtue of S’s having reason(s) R, and S believes p on the basis of R, then S’s belief that p is doxastically justified. I then propose and evaluate alternative accounts of the relationship between propositional and doxastic justification, and conclude that we should explain propositional justification in terms of doxastic justification. If correct, this proposal would constitute a significant advance in our understanding of the sources of epistemic justification.

Reasons, Perceptual Grounds, and Normative Explanation

Reasons come in many forms. There are reasons to believe, for believing, for which one believes, and why one believes; and some are internal reasons we have, others external reasons we lack. This chapter clarifies how we have normative reasons for beliefs in virtue of certain experiential states that ground those reasons: these states, including sense-experiences and hedonic experiences, are the kinds that ground the rationality of beliefs or the desirability of acts. Normative reasons, practical as well as theoretical, are themselves grounded in certain experiential elements, including perceptions as a central kind. Normative reasons for belief are unified by their explanatory scope: they can explain propositional justification—roughly, justification that at least permits our properly believing propositions adequately supported by our experience. These normative explanations parallel causal explanations that hold between the experiential elements, such as perceptions, that ground the reasons and the doxastically justified beliefs that reflect those experiences.

First-order justification logic with constant domain semantics

Justification logic is a term used to identify a relatively new family of modal-like logics. There is an established literature about propositional justification logic, but incursions on the first-order case are scarce. In this paper we present a constant domain semantics for the first-order logic of proofs with the Barcan Formula (FOLPb); then we prove Soundness and Completeness Theorems. A monotonic semantics for a version of this logic without the Barcan Formula is already in the literature, but constant domains require substantial new machinery, which may prove useful in other contexts as well. Although we work mainly with one system, we also indicate how to generalize these results for the quantified version of JT45, the justification counterpart of the modal logic S5. We believe our methods are more generally applicable, but initially examining specific cases should make the work easier to follow.

Imagination Cannot Justify Empirical Belief

A standard view in the epistemology of imagination is that imaginings can either provide justification for modal beliefs about what is possible (and perhaps counterfactual conditionals too), or no justification at all. However, in a couple of recent articles, Kind (2016; Forthcoming) argues that imaginings can justify empirical belief about what the world actually is like. In this article, I respond to her argument, showing that imagination doesn't provide the right sort of information to justify empirical belief. Nevertheless, it can help us take advantage of justification that we already have, thereby enabling us to form new doxastically justified beliefs. More specifically, according to the view I advocate, imagination can contribute to one's satisfaction of the proper basing condition – which turns propositional justification into doxastic justification – but without conferring any new justification that the subject isn't already in possession of upon their beliefs. Very little attention has been devoted to the distinction between propositional and doxastic justification in the literature on imagination, and the view I here argue for takes up a yet-to-be occupied position.