Identify the formal fallacy committed in the following argument: All household pets are domestic animals. No unicorns are domestic animals. Therefore, some unicorns are not household pets.

The inference fails because a particular conclusion is drawn from two universal premises.

All household pets are domestic animals is A, No unicorns are domestic animals is E, both universal.

The conclusion Some unicorns are not household pets is a particular O that asserts existence.

On the Boolean reading universal premises carry no existential import, so they cannot support an existential claim.

Concluding about existing things from purely universal premises is the existential fallacy.