2. Every living substance has by its nature some actual vital activity always going on in it, although other activities are potential: thus animals are always repairing waste by assimilation of nourishment, though they do not always feel. But separately subsisting intelligences are living substances, and have no other vital activity but that of understanding. Therefore by their nature they must be always actually understanding.
2.96 : That Intelligences Subsisting apart do not gather their Knowledge from Objects of Sense
2.98 : How one Separately Subsisting Intelligence knows another