The following argument is valid:
- (Premise) When one gets one's just deserts, one gets what one deserves.
- (Premise) One can only deserve that comes from an agent or group of agents.
- (Premise) There are cases of getting one's just deserts such that unless there is a God, then what one gets does not come from an agent or group of agents.
- So, when one one gets one's just deserts, one gets something that comes from an agent. (1 and 2)
- So, there is a God. (3 and 4)
The basic line of thought is that one can talk about someone getting justice in cases where there is no human agency. But justice seems to be essentially the work of an agent or community. So either we are mistaken in talking of justice in such cases or we need to posit Providence (or aliens who work providentially, but the divine Providence hypothesis has other advantages).