Grim reapers have recently been employed in an argument against an infinite past (see here and here). I'd like to see if grim reapers may similarly be employed in an argument against uncaused beginnings.
I will begin with a preliminary comment about the modal reasoning involved in a grim reaper argument. Then I'll review the grim reaper argument against an infinite past. Then I'll present a new, parallel grim reaper argument against uncaused beginnings.
As I see it, the grim reaper argument against an infinite past is an instance of modal reasoning in which one attempts to subtract credence from a modal claim by "connecting it" with a modal claim that's evidently false. To illustrate, consider the following argument against the possibility of time travel:
(1) Suppose I could go back in time.
(2) Then I could go back to a time before I was born.
(3) If I could go back to a time before I was born, I could prevent my birth.
(4) If I could prevent my birth, then I could exist without having been born.
(5) I cannot exist without having been born.
(6) Therefore, I cannot go back in time.
In the above example, we start with a somewhat "unclear" (and controversial) modal claim about time travel and then attempt to connect it via a series of (arguably) plausible premises to a claim that is easier to assess. This argument is just an example. Even if this particular argument isn't sound, you get the gist of the strategy.
The gist (or outline) of a grim reaper argument against an infinite past is something like this.
Suppose an infinite past (infinite sequence of past events) is possible. Then it would seem to be possible for there to have been any combination of events throughout an infinite past. Thus, it would seem to be possible for there to have always been (say) a factory that each year produces a grim reaper (GR), which is a device set to produce a certain event--such as killing a poor guy named Fred--at a set time if and only if the grim reaper detects that this event hasn't already been produced. Moreover, any combination of sizes, locations, check-rates, and "attack" times would seem to be possible (to avoid arbitrary modal cut-offs). Therefore, it would seem to be possible to setup a Grim Reaper scenario, which is a scenario in which the most recently produced GR is set to kill Fred at 12:30pm on date X, and each preceding GR is set to kill Fred at time 12:30pm - n / 2 on date X, where n is the number of years ago the GR was created. A GR scenario would seem to be impossible, however, because in it Fred dies at the hand of a GR by 12:30pm (since each is set to kill Fred before then--without prevention), yet no GR kills Fred (since a previous one would already have done so).
I'll call this style of argument 'Grim Reapers against an Infinite Past'--or 'GRAIP', for short.
I will leave open whether or not GRAIP is sound. Speaking for myself, I was agnostic about the possibility of an infinite past when I first encountered GRAIP, and GRAIP tipped me over into doubting that an infinite past is possible. So, the argument seems to have some merit (at least in my own thinking). That said, the argument is certainly not knockdown: one might resist one of the premises if one feels more confident that an infinite past is actually possible. But let us leave open for the sake of argument whether or not GRAIP is sound or in any way meritorious.
I'd like to consider whether GRAIP generalizes to produce other arguments for interesting conclusions. In particular, I am interested in the following conditional: if GRAIP is a good argument, then so is a grim reaper argument against uncaused beginnings--GRAUB.
Here is a gist (or outline) of GRAUB. Suppose uncaused beginnings are possible. Then it would seem to be possible for there to have been any combination of events (beginnings) that occur without a cause. Why should size or shape or degree of causal capacity of things that begin to exist make a modal difference here? It seems they wouldn't. Thus, it would seem to be possible for any number and any combination of GRs to come into existence uncaused. But then it follows that it would be possible for a grim reaper scenario to obtain without a cause. Thus, since a grim reaper scenario is impossible, so are uncaused beginnings.
This argument seems to me to be parallel to the original grim reaper argument. I propose, then, that if GRAIP is sound or meritorious, so is GRAUB. (And of course, if GRAUB is not sound or meritorious, then neither is GRAIP.)
I turn, finally, to another GR argument, which if parallel, may cause concern for some defenders of GRAIP. This argument (brought to my attention by a friend of mine) is basically this. Suppose God is omnipotent and so can produce at any moment any possible GR. Then God could produce at once any combination of GRs, including that combination which results in the paradoxical GR scenario. Therefore, an omnipotent God doesn't exist. Or: GRAIP is a bad argument (my friend's conclusion). Call this last argument 'Grim Reapers against God'--GRAG.
I am not sure what to think about GRAG. Is it parallel to GRAUB or GRAIP? Here is a reason one might think not. Perhaps God (unlike "nothingness" or an infinite past) is necessarily constrained by a rational nature not to produce contradictory scenarios. Furthermore, it may be that if God exists, then there is no possible omnipotent being distinct from God. If so, then we could explain why the GR scenario can't obtain in terms of the nature of the foundational element of every causal chain. Incidentally, this proposal seems to neatly fall out of Alex Pruss's theory of modality, according to which what is possible is grounded in the causal capacities of things within the actual history of causes.
Another idea (proposed to me by Alex Pruss) is that God operates trans-temporally and so doesn't make a fresh decision at every moment concerning what things to create. Uncaused beginnings, by contrast, don't operate trans-temporally.
Another idea is that there is a problem with producing an actual infinite number of events. This third idea, if correct, would seem to block the grim reaper argument against uncaused beginnings. But it would reinforce the argument for a finite past.
Your thoughts are welcome.