1. Historical survey. According to Aristotle, substance (οὐσία, ὑποϰείμενον) is the chief object of metaphysics (Metaphysics, VII, 1; 1028b, 2ff. and 6f.), because it is what primarily exists and is the first of the categories, to which all the others are intrinsically related. More precisely it signifies that which stands by itself, the ultimate bearer of all that belongs to a being (cf. Categories, I, 5; 2a, 11f.; 2b, 15ff.). This conception was further developed by the scholastics. It was opposed by the empiricism which was foreshadowed by Nicholas of Au…