In the present context we are concerned with the historical import of Hooke's procedure. This lies in the fact that, immediately after Descartes had satisfied himself that in thinking man had the one sure guarantee of his own existence, Hooke proved in a seemingly indubitable manner that thinking was entirely divorced from reality. It required only another century for philosophy to draw from this the unavoidable consequence. It appeared in the form of Hume's philosophic system, the outcome of which was universal scepticism.