Final answer:
Thomas Aquinas advocated against animal cruelty because it can lead to moral degradation in humans, aligning with the concept of a natural moral order and the belief that harming others ultimately harms ourselves. This belief supports the maintenance of human virtue and highlights the importance of humane treatment for all creations.
Step-by-step explanation:
Thomas Aquinas stated that people should avoid being cruel to animals because such cruelty can lead to desensitization and may foster a wider acceptance of inhumane behavior, potentially harming human society. Aquinas believed in a natural moral order set by God, and that by studying the inherent nature of beings, one can discern what is good for them.
Additionally, the gradual erosion of moral sensibilities through the tolerance of animal cruelty aligns with the broader philosophical concerns of how engaging in or condoning harmful practices can lead to corruption of character, as noted by Socrates. Thus, avoiding cruelty to animals is not just a matter of their welfare, but also of maintaining human virtue and moral integrity.