The phrase, 'realisation of a species type,' or 'fitness for the species' (congruentia speciei), in this chapter, points, not the attributes which a man should have to make him a good man, but the attributes that he actually has and must have by the fact of his being a man at all. -- With regard to dogs, horses and other 'educable' animals, who come to possess individual characteristics of their own, St Thomas would say that any dog or horse, so born, so bred, so circumstanced, would behave just as this or that dog or horse behaves. Determinists say the same of man: but St Thomas, not being a determinist, would deny it of man. Under determinism, all St Thomas's argumentation of a special divine providence over each individual man falls to the ground. According to St Thomas, a man using free will is an original, not merely one of a tribe. Originality is lost in determinism, and all true individuality; and no difference between man and man is left beyond the difference of one piece of iron hammered into the shape of a crook and another into the shape of a cross.
Of God and His Creatures: 3.113