Full Idea
In traditional logic from Aristotle to Kant, universal sentences have existential import, but Brentano and Boole construed them as universal conditionals (such as 'for anything, if it is a man, then it is mortal').
Gist of Idea
Traditionally, universal sentences had existential import, but were later treated as conditional claims
Source
Alex Orenstein (W.V. Quine [2002], Ch.2)
Book Reference
Orenstein,Alex: 'W.V. Quine' [Princeton 2002], p.15
A Reaction
I am sympathetic to the idea that even the 'existential' quantifier should be treated as conditional, or fictional. Modern Christians may well routinely quantify over angels, without actually being committed to them.