Tusi wrote a compact treatise on establishing the existence of a being separate from matter that is the ground of the truth of our necessary judgments. Here’s my summary of his argument:

A necessary truth is one whose truth-value can’t change. Now, where *p* (= belief, judgment, proposition, statement) is necessarily *true*, concede this: *p* is true iff *p* corresponds to something.

This something then, call it *x*, to which *p* corresponds, either exists (1) outside the mind or (2) it doesn’t. If (2), it follows that *p** (where *p** is a *false* judgment, belief, proposition, statement) is true; for *p** also has something corresponding to it in the mind. But that’s a contradiction. Therefore, *x* exists outside the mind.

As external to the mind, *x* is either (1.1) self-subsistent or (1.2) inheres in another being. If (1.1), *x* is either (1.1.1) spatio-temporally located or (1.1.2) not. If (1.1.1), *p* would not be, contra what was assumed, *necessarily* true. But that’s a contradiction. If (1.1.2), *x* would be a Platonic Form. But there are no such entities. Therefore, (1.2) *x* inheres in another being outside the mind.

This other being *x* inheres in is itself either (1.2.1) spatio-temporally located or (1.2.2) not. If (1.2.1), *x* would inherent its spatio-temporal condition; *p* would then, again, not be necessarily true – a contradiction. Therefore, (1.2.1) *x* inheres in another being that is not spatio-temporally located.

Salaam,

Sorry to comment on an old post. If we grant this proof, all it shows is that an intellect exists for all our propositions but why can this not be the intellect of God rather than the active intellect?

Also why would the spatio-temporal location influence the necessity of truth value of the proposition if self subsistent or inhering in another being. Suppose P is all bachelor are unmarried and suppose it existed in a particular location eternally? I understand why temporality would alter truth value but what if we grant it an eternal location?

salam akhi,

first, ramadan karim to you and yours. second, i was London a few days ago, and was down to meet up but, alas, couldn’t find you on FB.

anyway, regarding your first question, Tusi actually deals with it in the same Treatise just right after establishing the AI. the gist of his argument against God grounding the truth of necessary propositions is that that would compromise His simplicity.

as for your second question, it is because p’s truth would be contingent on the particular spatio-temporal location in question, whether or not that s-t location is eternal. the upshot: p would in fact be contingently true, not necessarily true, which contradicts the initial assumption.

btw, i have an article forthcoming where i translate (it’s fairly short) and offer a commentary on the entire Treatise.