I've learnt to articulate it a bit better since we last spoke about it:
Only human beings can 'act'.
When we say act, we mean to say:
•Aiming at ends.
•Understanding the concept of scarcity in the means available to achieve those ends, like time, energy, resources, capital, etc.
•Choose the preferrable ends and means by rank ordering them.
•Bear the opportunity costs of aiming at certain ends and means over others.
•Choose the preferrable ends and means based on costs.
•Take the risk of incurring a loss by choosing the wrong means to achieve their ends.
This is basically the action axiom.
Wading further into the philosophical territory, we can say that only human beings can 'reason' about things.
H/T Hans-Hermann Hoppe. His writings have helped me understand the above.
Furthermore, perhaps a theological argument can be made that only human beings have the ability to access 'revelational knowledge'. Only they have the gift of self-realization. But I am too young and inadequately read to elaborate this particular point properly.