A second hypothesis is that both agents will incompatible outcomes but neither obtains what was willed. In the traditional presentation, this is said to entail their incapacity: each fails to produce what he wills.
The inference is strongest when both are hypothesized to possess truly unrestricted power and when each intended outcome is possible when considered separately. However, “an outcome fails to occur” and “the agent is necessarily incapable in every respect” are not verbally identical propositions.
The inference to incapacity therefore requires attention to why the outcome fails, not merely the observation that it does not occur.