The value of information and the epistemology of inquiry

In the analytic tradition outside the philosophy of science, epistemology has typically begun at the point at which we have our evidence; it has then asked which beliefs or credences are justified or warranted by that evidence, which are rational and which count as knowledge for someone with that evidence. And yet we are not mere passive recipients of our evidence; we often actively collect it, and collect it in one way rather than another, or act in ways we know will bring us certain pieces of evidence and not others, even when acquiring that evidence is not the primary aim of that act. In this essay, I present and apply a theory that says when we should inquire and how. It is a probabilistic theory: I use probabilities to represent the opinions of the inquirer. And it is teleological: whether we should inquire in this way or that or not at all is determined by the value of the available options, where the value of an inquiry is determined by the value of the option you choose from the point of view of the opinions you have after the inquiry, the purely epistemic value of those opinions, the costs the inquiry incurs, and any other benefits it might bring. The theory says you should choose whether, when, and how to inquire just as you choose whether, when, and how to do anything else, namely, by maximizing value in expectation. This theory has its origins in Janina Hosiasson’s work in Bayesian philosophy of science in the 1930s and David Blackwell’s work in economics in the 1950s. In the first part of the essay, I present this theory in a way that assumes no prior familiarity with Bayesianism or the epistemology of probabilistic opinion more generally. In the second part, I put the theory to work. First, I extend it to cover not only inquiries in which you gather empirical evidence, but also those in which you undertake logical or conceptual reasoning. This allows us to ask, for instance, when we should spend our time gathering new evidence and when we should spend it drawing out the consequences of the evidence we already have. Next, I ask when the normative status of the inquiries that have led to our current opinions affect the normative status of those opinions. And finally I show how the teleological approach might be extended to furnish norms for other cognitive acts and processes, such as forgetting or coarse-graining a credal state so that it becomes a belief.