## Sunday, November 27, 2011

### A simple definition for truthmaker?

Brightly suggests a rule for finding a truthmaker for any proposition p, viz., any entity t such that 't exists' entails p will do the job. Thus we have an 'equation' to solve. When p = 'Vallicella exists' a solution would appear to be t = Vallicella.

I'm not sure that will do. For a start, it suggests that every truthmaker T of a non-existential proposition is a truthmaker for at least two propositions, namely the non-existential one, and also the existential one 'T exists'. E.g. let T be the truthmaker for 'it is day'. Then it is the trutmaker for that, and also the truthmaker for 'T exists'.

Also, more worryingly, the entailment relation is very easy to satisfy. If p is true, then its truthmaker is any (existing) entity x whatsoever, since x exists, and p is true, i.e. if x = a then 'a exists' and p are both true, and we have entailment. Entailment only failing when the antecedent is true and the consequent false. (I think, I always get lost with entailment).

#### 9 comments:

Anthony said...
This comment has been removed by the author.
Anthony said...
This comment has been removed by the author.
Anthony said...
This comment has been removed by the author.
Anthony said...
This comment has been removed by the author.
Anthony said...

Entailment is meant to indicate more than just "not p or q", though exactly what it is is hard to pin down.

However, I believe that Brightly's rule has to be modified. It is not enough for "t exists" to entail p. p must also entail "T exists". Otherwise existence would be the truthmaker of every true proposition. (Or, if you'd prefer, the set of everything that currently exists would be the truthmaker of every true present-tensed proposition.)

"I always get lost with entailment."

You agree that an argument can have a true premise, and a true conclusion, but still be invalid, right?

An argument is valid if and only if the premises entail the conclusion.

Of course, this is what I believe Brightly is referring to when he says that it is "the kind of thing that gets us into really hot water". Entailment, in this sense (as opposed to the many-worlds modal sense), is epistemological, not metaphysical.

Personally I think that's okay, though. It just means that the concept of truthmakers is an epistemological concept, and not a metaphysical one.

Anthony said...

"It is not enough for 't exists' to entail p. p must also entail 'T exists'."

Although, if you do that, then there is no truthmaker for "some man exists". I believe that according to truthmaker theory, every man is a truthmaker for "some man exists". A truthmaker is sufficent, but not necessary.

But then you get back to the universe being a truthmaker for every proposition about the universe.

So once you get past the simplest of propositions, I guess entailment isn't enough to explain truthmaking.

J said...

Some prefer alpine landscapes to desert, but ..Quine at least accepted the "posit" of scientific realism, ie, truthmakers (tho' many forget Quine also had pragmaticist roots, ala Peirce and would grant that in many instances something like..functionalism applies, rather than mere positivist Truth. Not ..is X true, but does X work--and can that be measured, proven to hold over many instances, etcetc. Platonists might not approve. Bridgebuilders do.

David Brightly said...

For BV, entailment is 'necessary implication'. See my 6:14pm comment on Friday's 'Socrates' post.

J said...

When p = 'Vallicella exists' a solution would appear to be t = Vallicella.

More like, the observation/confirmation of V's existence (within a certain domain, say Arizona), translated into the proposition "V. exists" and assigned "Truth". We're dealing with humans with a language (and word aka "Truth"), not hard drives. The implication just obscures the problem (ie, more like ...definite description in philosophaster language).