Jeff Sanford Russell
My research focuses on issues at the intersection of metaphysics, philosophy of physics, and philosophical logic. I am also interested in formal epistemology, philosophy of language, philosophy of mathematics, and philosophy of religion.
- Frege's Foundations of Arithmetic (syllabus / week 2 handout / week 4 exercises / week 6 handout)
- Introduction to Logic (notes to be posted eventually)
- Advice for writing philosophy papers
My research interests generally fall at the intersection of metaphysics, philosophy of physics, and philosophical logic—especially issues connected to possibility, space and time, and the relationship between particular individuals and their general features. Lately I've also been doing work in formal epistemology and philosophical applications of category theory.
- Groupthink (with John Hawthorne and Lara Buchak; forthcoming in Philosophical Studies)
Suppose several individuals with different credences (but the same values) need to jointly make some bets. A variation on a standard Dutch-book argument shows that their group betting pattern should be representable by group credences, which should be updated by conditionalizing on new evidence. Taking conditionalization as a basic constraint, we gather some lessons from the mathematical literature on credence aggregation. We then prove two new impossibility results, consider two kinds of credence-aggregation rules that satisfy some natural constraints, and give a general characterisation of the family of rules that use geometric averaging.
Leibniz gave a famous "shift" argument against the reality of absolute space. Some philosophers reply by appealing to anti-haecceitism about possible worlds. But it is difficult to understand that doctrine, and how it bears on the metaphysical issues at hand. It turns out that the best way of making sense of the relevant kind of anti-haecceitism is one that really concedes the main point of the Leibnizian argument.
David Lewis holds that a single possible world can provide more than one way things could be. But what are possible worlds good for if they come apart from ways things could be? We can make sense of this if we go in for a metaphysical understanding of what the world is. The world does not include everything that is the case—only the genuine facts. Understood this way, Lewis's "cheap haecceitism" amounts to a kind of metaphysical anti-haecceitism: it says there aren't any genuine facts about individuals over and above their qualitative roles.
Allen Hazen, Michael Fara and Timothy Williamson, and Delia Graff Fara have raised problems for David Lewis's counterpart theory: there is no obvious way to interpret modal language that uses an actuality operator in terms of counterparts. I show how this can be done after all.
Could space consist entirely of extended regions, without any regions shaped like points, lines, or surfaces? Peter Forrest and Frank Arntzenius have independently raised a paradox of size for space like this, drawing on a construction of Cantor's. I present a new version of this argument and explore possible lines of response.
Work in progress (comments welcome!)
I argue that those who accept that the world is ultimately qualitative have a reason not to be satisfied with a metaphysical theory expressed in the standard quantificational idiom. As part of making that case, a second goal is to articulate a vision of what it might take for a theory to be a “metaphysically perspicuous” account of the world.
- Space-Time Categories
Suppose we take the lesson of the hole argument seriously: there is no genuine difference between possible worlds related by a space-time diffeomorphism. In that case, what should we think the world's genuine space-time structure is like? It won't include facts about field-values at particular points in a manifold. Instead what we want is a precise account of "structural roles" for things like fields in space-time, understood in terms of their essential relationships to one another and contingent patterns of "coincidence" between different roles. Ideas from categorical logic give us the resources to spell out such an account.
"Pragmatic encroachers" about knowledge generally advocate two ideas: (1) you can rationally act on what you know; (2) knowledge is harder to achieve when more is at stake. Charity Anderson and John Hawthorne have recently argued that these two ideas may not fit together so well. I extend their argument by working out what "high stakes" would have to mean for the two ideas to line up, using decision theory.
- Temporary Safety Hazards
I consider two epistemic objections to certain "A-theories" about what temporary facts there are. The first is the "how do you know you're present?" objection to "growing block" and "moving spotlight" views. The standard presentations of this argument rely on epistemic premises that are far too strong, with sweeping sceptical consequences. So I reconsider this argument in a safety-based framework, arguing that beliefs about which time is absolutely present are unsafe (even if true), and thus don't amount to knowledge. The second argument is the objection from special relativity against presentism. I argue that this is also best understood as a sceptical argument with the same general form as the first: beliefs about temporary facts about things' three-dimensional shapes are unsafe (even if true). Understanding the similar structure of the two arguments especially squeezes presentists who are impressed by the first argument but not the second.
I am also working on a project about applications of category theory to the foundations of probability.