 Buridan’s view is neater.  He holds that when engaged in scientific theory, the subject matter is not limited to presently existing things.  Instead, the propositions have their usual meanings, but an expanded subject matter.  When the word ‘human’ is used, one is discussing every human, past and future, and even possible humans. [Buridan SdD 4.3.4] With such an understanding, the subject of ‘Every human is an animal’ is not empty at all.