Thank you.
Well, that is a definition, all right. But unfortunately there are many meaningless words in it, like: “grace, supernatural state, heavenly destiny, soul or supernatural invitation”. I have no idea what these mean. On the other hand “capable of rational thought and voluntary decision” I can understand very well. The trouble is that these attributes do not necessarily belong exclusively to biological humans.
Maybe it would be easier to start with something simpler. What is the “nature” or “essence” of a chair? Or maybe a “cow”? But only if you are so inclined. Don’t want to deviate from the topic too far.