How can something be animated while lacking an anima? It may lack a rational soul, as some argue, but to be alive and yet lacking a soul seems to contradict our working definitions of soul and life.
The soul, like a black hole, is inferred by reason. While we can observe the effects (animations), we cannot observe the efficient cause (anima) for those effects, e.g., the cause for a hole in space or what makes a dead dog immediately different than a live dog. In reality, the soul and the black hole exist or do not exist whether we think they do or not. The soul and the black hole are objects of reason (not observation) and provide explanatory power for things we do observe.
A property of living things that we observe is self-movement. If it moves we infer a soul. Does the heart in a box evidence self-movement? To answer, one would have to pull the plugs, so to speak, and observe. When the heart no longer moves I think all would agree the heart is not living, But what if the heart does not immediately stop?
If the heart does not stop beating rhythmically then is that movement evidence of the heart’s soul? Or is it merely the inertia of the soul of the living being from whom that heart was taken slowly ebbing away? I think so. If the heart continues to beat but does so arhythmically then is not the movement we observe the disorganized movement of individual cells now moving according to their own nature? (Just as cardiac cells in a petri dish would move). If the heart’s movements are random then I believe the human soul, the organizing principle of those multiple organs that constitute a heart, is no longer present. The individual organs or cells are “now free to move about the cabin.”
Since a soul in cases of things that self-move is inferred, no one can prove that the soul is of one kind or another in the absence of additional evidence of sentience (animal) or reason (human). In the absence of proof of human life are we allowed to act as if there is no human life? Can we infer death just as we infer life? If we may then ought we to exercise extreme care before acting in a way that ends a life? Kreeft, the ethicist, asks, “Does the hunter who is uncertain whether the object in the bushes is a deer or a man have the right to shoot?”
I think the church teaches in the case of the beginnings of human life that science’s tentative (as are all scientific) conclusions never justify taking that life. But in the case of the end of human life the church allows medical science greater latitude. My understanding is that the teaching remains that death occurs when the soul departs. While the church does not allow science to apply its findings to determine the beginning of life as ever subsequent to conception, she does allow science to determine the end of life prior to the absence of the normal palpable signs of life.