It has become common, in both popular and scholarly discourse, to appeal to ‘delayed animation’ as an argument for abortion (DAAA). Augustine and Aquinas seemingly held that the rational soul was infused midway in pregnancy, and therefore did not regard early abortion as homicide. The authority of these thinkers is thus cited by some contemporary Christians as a reason to tolerate or, for proportionate reasons, to promote first-trimester abortion and embryo experimentation. The present essay is an exercise in aetiology. It (...) examines the origins of DAAA. Distinctions are drawn between different forms of DAAA in historical context, premises, and conclusions. Some forms raise important anthropological questions, though these arguments are not indefeasible. The most popular forms of DAAA, which are typically framed as appeals to precedent, are the weakest, in that there is little precedent for DAAA before 1950. The argument is in fact a novelty in the tradition. (shrink)