Self-Consciousness, As Manfred Frank has succinctly put it, is the name of a philosophical problem. The problem centers on whether knowledge claims can be advanced on the basis of self-conscious awareness, or, stated in reverse, whether the data of self-consciousness can lead to knowledge. A key moment in this philosophical discussion was reached when Descartes discovered an inviolable defense (or so he thought) against seventeenth-century skeptics, the (latter-day) Pyrrhonists. This was the cogito ergo sum, an argument that proceeded on the basis of the self-evidence of internal states of self-awareness. Descartes held the existence of these internal states at bottom to be beyond doubt, effectively conscripting them in the service of a new knowledge paradigm. Two traditions of thought — Cartesian rationalism and empiricism — emerged in the wake of this argument, the one sniping at the other across a mental and sometimes also cultural divide, neither tradition on its own being able to refute entirely the claims of the other, each standing its ground with resolute solemnity. This was the state of affairs until the arrival of Immanuel Kant, who only learned to appreciate the one-sidedness of his own relation to Cartesian thought when confronted with key objections expressed on the other side, notably by the Scottish skeptic David Hume. Hume’s empiricist challenge to the Cartesians denied any connection between mental states and the actual constitution of the outside world. But this also meant that empiricism, for its part, could not postulate any more than disconnected existences in the world. Kant’s importance lies above all in his attempt to solve Hume’s problem of disconnected existences — a problem that from the opposite viewpoint was also Descartes’s (and, in this same tradition, Leibniz’s), namely how to reconcile the inner mental states arising from our individual “monadological” being in the world with the empirically objective sense of the being of that world. Before the advent of Kant’s later critical philosophy, the rationalists stood implacably opposed to the empiricists, while both in turn and in their own way opposed the supernaturalists, for whom all knowledge was knowledge of the divine, and the skeptics, who denied all such knowledge and, in extreme cases, the ground of all knowledge itself.