Name the fallacy in: 'All men who understand women are potentially perfect husbands. All potentially perfect husbands are men of infinite patience. Therefore, some men of infinite patience are men who understand women.'

Two universal premises cannot support the particular conclusion drawn here.

Both premises are universal affirmatives, which assert no existence on their own.

The conclusion 'some ... are ...' claims that a thing actually exists.

Drawing an existence-claiming particular from purely universal premises is unwarranted.

This leap is the existential fallacy.