Single Culprit Fallacy

Consider the following argument.

Proposition 1 is clearly true. For a crime to be committed someone must commit it, and we call that person a criminal. Proposition 2 is also true. According to the Austin Police Department, tens of thousands of crimes (of one sort or another) occur in the city every year. Moreover, the premises are related to one another such that we could deduce some conclusion from them, but the Inference A is clearly a non sequitur: the premises give us no reason to believe Proposition 3.

From the premises we can conclude that there are criminals in Austin or at least that there were at some point during the year. Someone must have committed the crimes. But we can't deduce that there was any single criminal that committed all the crimes. The premises don't give us any information about how many of the crimes were committed by the same person. For all they say, every crime might have been committed by a different criminal. And, going by our background knowledge of criminology, this is a lot more likely than that there was some single master criminal who committed every crime in town. More likely than either of these alternatives is that there were many criminals, and that some of them committed multiple crimes. Any judgment we make about how many criminals there probably were is going to depend on such background knowledge, nothing in the premises suggests one way or another, and the premises certainly don't give us any reason to think that the crimes were all committed by one person.

This argument commits what we can call the single culprit fallacy. Let's describe it more generally. One premise tells us that a phenomenon of a certain sort (e.g. crime) cannot exist without a being of a certain sort (e.g. a criminal) to cause it. The second premise tells us that phenomena of that sort do exist. Then the conclusion says that there is a being of the relevant sort that causes all of the relevant phenomena.

We could conclude from the premises that at least one being of the relevant sort exists, but not that there's a single such being causing all of the relevant phenomena. That's a non sequitur. To reach any conclusion about how many such beings there are, and about which of the phenomena are caused by the same being (and which by other beings of the same type) we'd need more information than is included in these premises.