What distinguishes people from animals?

Arcana Coelestia 5302 provides a nice short explanation of what makes a person different from an animal.

Stupid people suppose that man is man from his outward form, in that he has a face like a man's; those less stupid say man is man because he can speak; and those still less stupid, that man is man because he can think. But man is not man from these things, but from the fact that he can think what is true and will what is good, and that when he thinks truth and wills good he can look up to the Divine and perceptibly receive it. It is in this that man is distinguished from the brute animals.