Brains, Persons, and Society *** ABSTRACTS    Cervelli, Persone e Società ***ABSTRACTS

Sebastiano Moruzzi

Arché AHRC Centre, St Andrews

Vagueness and Omniscience

The paper explores the consequences of the notion of omniscience for vagueness in relation to the

supervaluationist approach.

Why is the notion of omniscience relevant to the problem of vagueness?

John Hawthorne suggests that the notion of omniscience is relevant of the problem of vagueness because

since no boundary in the sorites series seems hidden to us, we are in a position to know everything in

relation to the application of the relevant vague predicate. Omniscience functions thus as a useful

abstraction to test the coherence of any conception of vagueness which is committed to the idea that

vague predicate are boundaryless , (Hawthorne (2005) p. 9).

Following a suggestion made by Cian Dorr, a semantic theory of vagueness can be seen an instance of

the the so-called “no-ignorance theories” about vagueness. According to these theories, unwillingness

to assert “p” and to assert “not-p” when “p” is borderline entails that it is not the case that we are

ignorant as to whether p. (Dorr (2003) p.87). In borderline cases there is is nothing to be ignorant of,

we are thus in shcu cases in the same position of an omniscient being.

Vagueness can be introduced in connection to the notion of the borderline cases, and borderline cases

can be suitably introduced by ostension (I will not pursue attempt to define these notions). Thus I

will delimit the application of “vague” to atomic sentences where the subject is a borderline case of

the predicate: to say that it is vague whether Bob is bald, it is to say that Bob is a borderline case of

baldness.

Now, several semantic account of vagueness connect the notion of vagueness to the notion of semantic

indeterminacy. According to this cluster of theories, vagueness is a peculiar case of semantic indeterminacy.

Thus, for example, if it is vague whether Bob is bald, then it is indeterminate whether bob is

bald - where to say that it is indeterminate whether Bob is bald is to say that is indeterminate that Bob

is bald and that Bob is not bald. Generalising, we have:

(Indeterminate whether) : p is indeterminate whether p iff (it is not determinate that p and it is not

determinate that not-p)

(Vagueness) if it is vague whether p, then it indeterminate whether p

The second principle I want introduce is a well-known principle that connects vagueness to ignorance.

Consider again Bob who is borderline case of “bald”. By (Vagueness) the semantic theorist holds that

it is semantically indeterminate that Bob is bald. How does this indeterminacy hinge on our knowledge

that Bob is bald? Given Bob’s scalp and the actual meaning of “bald”, there is no fact - linguistic or not

- to appeal to in order to establish whether Bob is bald, therefore there is nothing to know about Bob

which could provide us knowledge of whether or not he is bald - that is to say, there is nothing to know

about Bob’s baldness. The supervaluationist seems then to be committed to the ignorance principle that

indeterminacy entails lack of knowledge:

(IP) Necessarily, if it is indeterminate whether p, then no one knows that p

In the paper, followong Hawthorne, I consider three definitions of omniscience and I highlight problems

for all these definitions (showing in detail why, under minimal assumption for the logic of “definitely”

all these definitions are inchoherent with the prvious principles) .

The paper concludes suggesting that we are not in a position to know that omniscience is possible, we

too readily come to accept omniscience is possible because of a misapprehension of the phenomenology

of vagueness. Hawthorne’s motivation of the relevance of omniscience for the problem of vagueness

relies on a consideration about our epistemic situation in a sorites series.

What Hawthorne is entitled to say is not that since we lack any view on the matter, we consequently

lack any evidence on any aspect of the matter - e.g. that, in relation to baldness, we lack on the existence

of a boundary. The explanans must be a different one, but which? A suggestion to find the right one

lies in a proper appreciation of the nature of our hesitance, which could even lead to suspension of

judgement, that we characteristically feel when faced with borderline cases. The nature of this kind

hesitation seems to be constrained by three principles:

Insufficiency : if a thinker takes a view, the evidence he could possibly exhibit for his judgement is of a rather

peculiar sort: it is not sufficient to dismiss someone else view;

Objectivity when the view is held, it counts as, from the point of view of the thinker, the correct view;

No-Ignorance the insufficiency of the evidence is not prima facie explicable in terms of probabilistic evidence

or, more generally, insufficient evidence of certain fact which we are ignorant of to certain extent

(see Schiffer (2003)).

In the paper I try to show that, under the above description of the phenomenology of vagueness the

fact that we are in this epistemic consideration is not something constitutive of the cases of application

vague predicates qua borderline cases, rather it is, so to say, a byproduct, of the interaction of two

phenomena: being presented in front of borderline cases and being engaged in a sorites reasoning. If

these two phenomena happen to occur together, then our epistemic situation does indeed happen to be

such that we are omniscient simply because there is nothing to know, justifying then the claim that

vague predicates are boundaryless.

The harmless thought that vagueness entails lack of ignorance of any boundaries in a sorites series

becomes the dramatic thought that vague predicate are boundaryless and thus the unwarranted claim

that even an omniscient being would not be in a better epistemic position than a normal thinker in

respect to the knowledgeability of a boundary in the sorites series.

References

Dorr, C. (2003). Vagueness Without Ignorance. In J. Hawthorne and D. Zimmerman (Eds.), Language

and Philosophical Linguistics, pp. 83–114. Blackwell.

Hawthorne, J. (2005). Vagueness and the mind of god. Philosophical Studies 122(1).

Schiffer, S. (2003). The Things we Mean. Oxford University Press.