This paper addresses a difficult passage from Aristotle’s Metaphysics (V. 4, 1015a11-13) in which he identifies a metaphorical use of the term “nature” (phusis) to refer to the entities which he calls “substances” (ousiai). I claim that the passage at stake deploys the very notion of metaphor on the basis of an analogy (as defined in the Poetics and in the Rhetorics), which is grounded on a weak (and, sometimes, very weak) similarity between two relations (each involving two relata). The (...) sentences found in 1015a11-13 belong to those kind of metalinguistic sentences which we usually employ to shed some light on the metaphorical use of a term. The similarity Aristotle is presupposing is this: both nature and substance are, in their respective fields, some kind of principle that guarantees (besides other things) certain persistence conditions for what they are the principles of. And this weak similarity is enough for the term “nature” to refer metaphorically to substances. (shrink)