In his discussion in Laokoon of the limits of poetry Lessing declares that detailed description of bodies in space is unpoetical. He justifies his contention that progressive actions are the peculiar subject of poetry by reference (1) to the means of poetry and (2) to the practice of Homer, all of whose descriptions he affirms are progressive. Many critics have not been satisfied with Lessing's limitation of poetry to progressive actions, and have attacked his conclusions by showing (1) that his conception of the means of poetry is inadequate, (2) that Homer contains a number of descriptions of objects in space. Taking as a starting point Lessing's position in regard to these descriptions, I think it possible to explain on a psychological basis the reason for Lessing's assertion that the poet would better not attempt to describe objects in space, except by the Homeric device of substituting progression for co-existence.