Like most of his contemporaries, the American physician and poet William Carlos Williams regularly wrote criticism on the work of other poets of his generation. Like many modernists, furthermore, he took an interest in science and saw the potential of scientific advances for reconceiving writing in general and poetry in particular. In fact, literary criticism and science are to some degree interrelated in Williamss thinking. This article examines Williamss writing on the work of Gertrude Stein and Marianne Moore and how these two poets are used in formulating his own poetics. Several of Williamss literary works engage with science, but his criticism on Moore and Stein offers particularly interesting insights into his conception of the relationship between science and poetry. This relationship is not one of poetry borrowing from science, but rather one in which poetry emerges as a science in its own right.