Wednesday, March 8, 2023

Thomism and presentism

According to Thomism:

  1. That I exist is explanatorily prior to all the other facts about me.


  1. That yesterday I safely crossed a street is explanatorily prior to the fact that I presently exist.

  2. If presentism is true, the fact that I presently exist is the same fact as that I exist.

  3. There are no circles of explanatorily priority.

  4. That yesterday I safely crossed a street is a fact about me.

It logically follows from these that:

  1. Presentism is not true.

(For from 2 and 3, if presentism is true, that I safely crossed a street is prior to the fact that I exist. But by 1 and 5 that I exist is prior to the fact that I exist. If presentism is true, we thus have a priority circle, so by 4, we don’t have presentism.)


Wesley C said...

Couldn't someone object that 2) equivocates or confuses the meaning of existence? Because 1) refers to the bare-bones fundamental possession of being at all, whilst 2) refers to your existence not qua possessing being fundamentally but as being alive

But being in the sense of 1) is basically the ACT of EXISTENCE one has, while 2) is one's existence in the more broad secondary sense of BEING ALIVE as a whole substance.

Michael Gonzalez said...

That the statement "I crossed the street safely yesterday" is a truth about anyone in existence is explanatorily posterior to my present existence. That someone crossed the street may not presume my existence, but that it was me (this person presently typing) presumes that there I exist.

As A. N. Prior always said, truths about the past/future are present truths about the past/future (viz., "it is true now that I crossed the street safely"). As such, the claim that this is true of me presumes that there presently is a me.

Another way to see this is to suppose that Bob did not cross the street safely yesterday and thus no longer exists. It follows that there is no "Bob" for whom it is true that they did not cross the street safely yesterday. Thus Bob's existence (or lack thereof) is explanatorily prior to the truthfulness of statements about him.

Alexander R Pruss said...


My mistake. Run the argument about some non-human critter that doesn't survive death.

ASBB said...

This is indeed a general problem, and as a presentist I have no fully satisfactory solution. Even just consider a case where my being green causes me to be square & red tomorrow, and my squareness tomorrow causes me to be green the day after. Plausibly, we just have a case of gappy existence of a single state of affairs - my-being-green which caused and was caused by my squareness. For some reason, this seems unobjectionable.

Perhaps some states of affairs cannot endure beyond an instant and cause exact duplicates? Then there are distinct greenness-es of myself. Applying that, could I have distinct existences? Perhaps what we could say is that there exist 2 states of affairs. My existence, and my present existence (the former enduring, the latter being a fleeting instantaneous state). The latter is explained by the safe street crossing. The former is explained only by God's creation of my soul and infusing it into my body.

I'm not completely satisfied, but it's just something I'm working with so far.

Alexander R Pruss said...


But now we have a circle of explanation. I (assuming for the argument I am the sort of critter who doesn't have a post-death existence) exist today because I crossed the street safely. But *I* crossed the street safely in part because I exist today. That's impossible!

Trevor Giroux said...

Dr Pruss, if a Thomist were to reject presentism what do you think the best view of time would be from a Thomist perspective?

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

This argument seems, in part, to be an alternative formulation of the existential inertia claim. Premise (2) should read: "That yesterday I safely crossed a street is *temporally* prior to the fact that I presently exist." But, the fact that I existed yesterday doesn't explain my present existence; God, as primary cause, does (unless by "explain" one simply means that it occurred previously).

Premise (3) is playing with language. When the presentist says "I exist" that includes an implied temporal reference to the present. So (3) should read, tautologically: "If presentism is true, the fact that I presently exist is the same fact as that I (presently) exist." What is specific to the presentist view is that only the present exists; not that one can make statements which lack a temporal reference refer to any time whatsoever. Thus the first half of the OP concluding remarks should read: "For from 2 and 3, if presentism is true, that I safely crossed a street is *temporally* prior to the fact that I (presently) exist."

To make the inference "But by 1 and 5 that I exist is prior to the fact that I exist," premise (1) must be interpreted as meaning that my present existence explains facts concerning my past. In that case it doesn't apply to Thomism. If (1) is interpreted as meaning act follows being or as pointing to the priority of substances or the priority of being, then it's compatible with Thomism. But the concluding remarks of the OP are reading way more into (1) than this.

Alexander R Pruss said...


If I am the kind of critter that does not survive death, then the fact that I safely crossed the street is not merely temporally prior to my present existence. I presently exist in part *because* I safely crossed the street. If we don't say this, then we have capitulated too much to occasionalism.

Don said...

As implied in the last paragraph of my previous comment, the type of explanation the past is doing for the present is different than the type of explanation my being is doing for me.

"I presently exist in part *because* I safely crossed the street." This is the claim of the proponents of existential inertia (minus the "in part" qualifier).

Don said...

Clarification: The quoted statement is a claim of existential inertia when the explanation referenced (the "because") is taken to be of a certain type.

Alexander R Pruss said...

Sure, it may be a different *type* of explanation, but it's still an explanation, and so it still generates a vicious circularity.

I know that it is sometimes said that it's OK to have a circle of explanations when the explanations are of different types. I think that's false, and I don't know of any cases that stand up to scrutiny.

Don said...

Where's the circularity? It's only circular if it's held that my (present) existence explains facts about my past. But this is not a principle of Thomism.