The hypostatizing of abstractions is the error against which Occam is continually fighting.
We define essences of course in a sense, but the essences of which men talk are abstractions, " creatures of the understanding."
When nominalism was revived in the 14th century by the English Franciscan, William of Occam, it gave evidence of a new tendency in thought, a distrust of abstractions and an impulse towards direct observation and inductive research, a tendency which had its fulfilment in the scientific movement of the Renaissance.
Seneca even made the discussion of such problems into a regular discipline, claiming that their concrete character gave an interest in morality to those who had no love for abstractions; while they prevented those who had from losing themselves in the clouds.
But this is precisely an instance of the hypostatization of abstractions in exposing which the chief strength and value of Nominalism lie.
