The main goal of this paper is to explore the continuity and discontinuity in
how different philosophical systems understand the concept of substance. At
the beginning of the paper, I draw a distinction between formal criteria for
what it means to be a substance and the question of what satisfies those
criteria. I then analyze Aristotle?s, medieval and modern views on substance
in order to show that, in spite of other considerable differences among them,
Aristotle, Thomas Aquinas, Duns Scotus, Descartes, Locke and Hume all
identify the same criteria for being the substenc. The differences between
them, I then claim, lie in the way they answer the question of what satisfies
the criteria. The most radical conclusion, as will be clear, is drawn by
Hume, who famously believes that there is nothing that really satisfies
traditional formal criteria for substantiality. In the last part of the
paper, I analyze Kant?s idealist view and show that it is his only within his
philosophical system that we can find a complete break with the philosophical
tradition and quite differing criteria for substantiality. It will be shown
that, for Kant, substance is no longer something that should be the basis for
the properties of objects that exist independently of us, but the way in
which human cognitive powers understand some key aspects of the
phenomenological domain of the knowable. The upshot of this discussion is
that the history of the idea of substance can be divided on the period before
and after Kant, where it is Kant, rather than Descartes, the one who truly
diverges from the traditional philosophical pardigms about substance.