These metaphysical entities, variously named Ideas, Notions, Concepts or Universals, may be divided into two kinds, sensuous arid supersensuous. The sensuous are those which may be apprehended by the senses, such as ‘red’, ‘cold’, ’round’, ‘swift’, ‘painful’, and the supersensuous, those apprehended not in sensuous perception but otherwise. Logical relations, ‘necessity’ or ‘impossibility’, and such ideas as ‘willing’, ‘end’, ‘ cause’, and ‘being three in number’, have in this way been supposed to be directly apprehensible by the mind. Amongst these supersensuous Ideas good is to be found.
Nothing could be simpler than such a view, and to many people the subsistence of such a property of goodness appears not surprising. But to others the suggestion seems merely a curious survival of abstractionism, if such a term may be defended by its close parallel with obstructionism. A blind man in a dark room chasing a black cat which is not there would seem to them well employed in comparison with a philosopher apprehending such ‘Concepts’.