This seminar will investigate the phenomenon of vagueness, with particular focus on the linguistic (semantic and pragmatic) questions that it gives rise to, but also with attention to the philosophical questions that have made it a topic of interest to philosophers for millennia. The central issues can be illustrated by considering the use of a predicate like is expensive in the following example:

  • The coffee in Rome is expensive.

The problem is that what exactly it means to 'count as' expensive is indeterminate; this indeterminacy gives rise to three kinds of phenomena. The first is truth conditional variability: this sentence could be judged true if asserted as part of a conversation about the cost of living in various Italian cities (In Rome, even the coffee is expensive!), for example, but false in a discussion of the cost of living in Chicago vs. Rome (The rents are high in Rome, but at least the coffee is not expensive!).

The second is the existence of 'borderline cases'. For any context, in addition to the sets of objects that a predicate like is expensive is clearly true of and clearly false of, there is typically a third set of objects for which it is difficult or impossible to judge. Consider, for example, a visit to a coffee shop to buy a pound of coffee. The Mud Blend at $1.50/pound is clearly not expensive, and the Organic Kona at $20/pound is clearly expensive, but what about the Rocket to the Moon Blend at $9.25/pound? A natural response is 'it depends' (on the price of other blends, on how much I am willing to spend, etc.); this is the essence of being a borderline case.

Finally, vague predicates give rise to the Sorites Paradox:

  • A $5 cup of coffee is expensive (for a cup of coffee).
    Any cup of coffee that costs 1 cent less than an expensive one is expensive (for a cup of coffee).
    / Therefore, any free cup of coffee is expensive.

The structure of the argument is valid, and the premises appear to be true, but the conclusion is without a doubt false. It is clear is that the problem with the argument lies somewhere in the induction built on the second premise; what is hard is figuring out exactly what goes wrong. Crucially, we not only need to explain the problem with the logic here --- assuming there is one, which is one of the questions to ask --- but also why we are so willing to accept the second premise as true.

The goal of the seminar will be both empirical and theoretical. On the empirical side, we will attempt to outline the 'boundaries of vagueness': how pervasive is it in language and what is its relation to other forms of semantic indeterminacy (ambiguity, imprecision, context-dependence, and so forth)? On the theoretical side, we will consider some of the main approaches to the phenomena outlined above (semantic, logical, epistemic, perceptual, contextualist, supervaluationist) and discuss their implications for semantic/pragmatic theory and the nature of linguistic meaning.


Below is the current plan (as of April 5), though it will remain flexible throughout the quarter. Please try to work through as much of the readings as possible before the class in which they will be discussed.