In book 3 of On Abstinence from Animal Food, Porphyry is traditionally taken to argue that animals are rational and that it is, therefore, unjust to kill them for food. Since the vast majority of scholars endorse this interpretation, I call it ‘the consensus interpretation’. Yet, strangely enough, elsewhere in his corpus Porphyry claims that the non-human animals are irrational. Jonathan Barnes notices this discrepancy and suggests that an appeal to the distinction between specific and non-specific predication can resolve the (...) problem. This paper explains Barnes’ solution, but argues that it must ultimately be rejected. It concludes with a brief survey of other approaches to the problem, and with an outline of the proposed solution, in which the consensus interpretation of On Abstinence is rejected in favour of a dialectical reading of Book 3. Porphyry, this piece suggests, may not have believed that animals were rational after all. (shrink)