The mystical title of this commentary on Professor Davies' provocative and timely key article is intended to emphasize my belief that many of the problems of attempting to relate biology to ‘aggression’ stem from deliberate or inadvertent reification. ‘Aggression’ is clearly a ‘concept’ and not an ‘entity’ and, as such, it is difficult to perceive the very diverse activities receiving this label as having a common physiology. Concepts are adopted (or eventually rejected) on the basis of usefulness not correctness. This is not to deny that any useful reference to aggression must concern animals, i.e., creatures with physiologies. Most individuals in their dispassionate moments would not regard the sea or a volcano as being aggressive and would certainly fail to apply this attribute to dry-rot fungus.