Online research in philosophy

Underdetermination is a relation between evidence and theory. More accurately, it is a relation between the propositions that express the (relevant) evidence and the propositions that constitute the theory. Evidence is said to underdetermine theory. This may mean two things. First, the evidence cannot prove the truth of the theory. Second, the evidence cannot render the theory probable. Let’s call the first deductive underdetermination, and the second inductive (or ampliative) underdetermination. Both kinds of claim are supposed to have a certain epistemic implication, viz., that belief in theory is never warranted by the evidence. This is the underdetermination thesis.

I want to discuss a problem that arises when you try to combine an attractive account of what constitutes evidence with an independently plausible account of the kind of access we have to our evidence. According to E = K, our evidence consists of what we know. According to the principle of armchair access, if a proposition is part of our evidence we ought to be able to know that this proposition is part of our evidence ‘from the armchair’. Combined, these claims entail that we can have armchair knowledge of the external world. Because it seems that the principle of armchair access is supported by a widely shared intuition about epistemic rationality, it seems we ought to embrace an internalist conception of evidence. I shall argue that this response is mistaken. Because externalism about evidence can accommodate the relevant intuitions about epistemic rationality, the principle of armchair access is unmotivated. We also have independent reasons for preferring externalism about evidence to the principle of armchair access.

How are reasons and evidence interrelated? According to one prevalent view, reasons and evidence are equivalent: evidence is a reason, and a reason is evidence. On another view reasons and evidence are conditionally related: if there is evidence, then there is a reason. On a different view reasons and evidence are disjunctively related: reasons or evidence can be substituted for each other. In this paper, I argue against these common views, and I defend the view that reasons and evidence are conjunctively related: evidence and reasons are distinguishable yet inseparable. I argue reasons and evidence are distinct because they come apart in certain cases, and I argue reasons and evidence are inseparable because only when properly conjoined are they capable of yielding correct verdicts on important cases in epistemology.

How are reasons and evidence interrelated? According to one prevalent view, reasons and evidence are equivalent: evidence is a reason, and a reason is evidence. On another view reasons and evidence are conditionally related: if there is evidence, then there is a reason. On a different view reasons and evidence are disjunctively related: reasons or evidence can be substituted for each other. In this paper, I argue against these common views, and I defend the view that reasons and evidence are conjunctively related: evidence and reasons are distinguishable yet inseparable. I argue reasons and evidence are distinct because they come apart in certain cases, and I argue reasons and evidence are inseparable because only when properly conjoined are they capable of yielding correct verdicts on important cases in epistemology.

Evidence-based policy is gaining support in many areas of government and in public affairs more generally. In this paper we outline what evidence—based policy is then discuss its strengths and weaknesses. In particular, we argue that it faces a serious challenge to provide a plausible account of evidence. This account needs to be at least in the spirit of the hierarchy of evidence subscribed to by evidence-based medicine (from which evidence—based policy derives its name and inspiration). Yet evidence-based policy’s hierarchy needs to be tailored to the kinds of evidence relevant and available to the policy arena. The evidence required for policy decisions does not easily lend itself to randomised controlled trials (the "gold standard" in evidence-based medicine), nor, for that matter, being listed in a single all—purpose hierarchy.

Some prominent accounts of scientific evidence treat evidence as an unrelativized concept. But whether belief in a hypothesis is justified seems relative to the epistemic situation of the believer. The issue becomes yet more complicated in the context of group epistemic agents, for then one confronts the problem of relativizing to an epistemic situation that may include conflicting beliefs. As a step toward resolution of these difficulties, an ideal of justification is here proposed that incorporates both an unrelativized evidence requirement and the requirement of the security of the evidence on which a conclusion from data is based. The latter requirement incorporates the consideration of epistemic modal statements.

In this note, I consider various precisifications of the slogan ‘evidence of evidence is evidence’. I provide counter-examples to each of these precisifications (assuming an epistemic probabilistic relevance notion of ‘evidential support’).

Abstract Evidence that supports a theory may be available to the scientist who constructs the theory and used as a guide to that construction, or it may only be discovered in the course of testing the theory. The central claim of this essay is that information about whether the evidence was accommodated or predicted affects the rational degree of confidence one ought to have in the theory. Only when the evidence is accommodated is there some reason to believe that the theoretical system was ?fudged? to fit the evidence in a way that weakens support. This weakening is an objective matter, but not one that can be conclusively determined by examining the contents of the theory and its logical relationship to the evidence. Consequently, there is less reason to believe a theory on the basis of that evidence when it is known that the evidence was accommodated than there would be if it was known instead that the same evidence had been predicted.

In Bayesian epistemology, the concept of one proposition’s being evidence for another is explained along the following lines. Given a measure of degrees of confidence, con(...), that conforms to standard probability axioms: (EV) a proposition e is evidence for a proposition h iff con(h|e) is greater than con(h). (Con(h|e) is the degree of confidence in h given e, and is defined as con(h and e)/con(e).) Proposals along these lines, however, have been dogged by what Clark Glymour called the Problem of Old Evidence.[i] (EV) apparently precludes a theory being confirmed by evidence that is already in. For if a potentially evidential proposition, e, is already known, then con(e)=1. One can be subjectively certain of propositions already known to be true. But by definition of con(h|e), where con(e)=1, con(h|e) will always be equal to, and hence never greater than, con(h). Not only does (EV) preclude one from confirming new theories on the basis of information already gathered. Suppose Q is some proposition of which we are now uncertain, but which is evidence for a scientific hypothesis P. That is, con(P|Q) is greater than con(P). If we now devise an experiment to test whether Q, perform the experiment, and become certain that Q, it will no longer count as evidence for P. Thus, if we accept (EV), gathering new evidence to support a theory actually has quite the opposite effect. Gathering the evidence destroys its quality as evidence.

The Requirement of Total Evidence (RTE) asks an agent to make her confidence in a belief proportional to the support it receives from her total evidence. This paper examines (RTE) as a norm of epistemic rationality and argues that it is problematic. Looking at the work of Peter Achinstein (2001) on the notion of evidence it becomes clear that (RTE) endorses a view of the constitution of evidence that is neither necessary nor sufficient for something to count as evidence. To overcome this and other deficiencies associated with (RTE) a move is made to an objective view of evidence. This move aligns epistemic rationality with scientific rationality in seeking to capture veridical evidence. It also leads to a new norm of epistemic rationality--the Proper Subset Evidence Requirement (PSER).