Following St. Thomas, we can construct a very fast and loose hierarchy of life-forms.
At the bottom are single-celled organisms that merely “live.”
On the next level are plants who possess only the “nutritive” or “vegetative” soul; they “grow.” Moreover, such organisms are multicellular and sport different organs.
Then there are animals like oysters that have senses but are immobile.
Then we have higher animals who “transcend space,” i.e., who can move about, like parrots and lions.
Up at the very top, we have humans who as rational animals transcend both space and time, i.e., are 4-dimensional, operating in all 4 periods, past, present, future, and timelessness.
To quote from my book,
… seeking narrow happiness by a vicious person is nugatory. For if later on in life Smith decides to “become a better person,” whatever exactly that entails for him, then he may have to reject, abandon, and purge those very desires that he struggled so valiantly to satisfy, making all his previous efforts entirely vain.
In other words, suppose Smith once felt that drinking himself into a stupor and wallowing in his own filth like a pig was a fine way of living. Then he wakes up and tries to pull himself together. Here’s the thing: recalling his past pleasures will not be a happy experience for Smith but rather full of shame and pain. The pleasures will be despised, and Smith will want to forget his past. It’s as if his past is condemned, and his very life thereby shortened.
Such will be the fate of all people without a coherent self.