The constraint on depicted moments follows from the nature of visual art as presenting a single instant, not solely from art's ultimate purpose.

Lessing does not appeal to any philosophical theory to back up this insistence. But his next step is to buttress his argument by borrowing Mendelssohn’s idea that since the visual arts present objects in a single moment, they must choose that moment carefully, and in particular they must choose a moment that gives “free rein” to the imagination. Even if it were to be conceded that “Truth and expression are art’s first law,” which Lessing is not actually willing to concede, this would still hold.