From the very outset Darwin’s extensive use of metaphor in the Origin has proved controversial, with some people thinking Darwin was thereby committed to ascribing intentions or even consciousness to nature, and others fearing that readers would be misled into thinking that he was. Also, some have argued (e.g. Gillian Beer) that Darwin should be regarded as much as a poet as a scientist. We argue that, on the contrary, his metaphors have a substantively scientific role, and do real work in the development of his argument. Firstly, as Darwin himself stresses, ‘such metaphorical expressions… are almost necessary for brevity’. Secondly, they provide a method for forming new concepts (as in the case of ‘struggle’). Thirdly, and, most significantly, the use of metaphor enables Darwin to explore further the analogy between NS and AS and directly compare the achievements of human breeding and those of the struggle for existence.