subtilisation

Still, in all this erroneous subtilisation, and these abortive efforts, Kant perceived a grasping at some real idea -- fugitive indeed and coy, which had for the present absolutely escaped; but he caught glimpses of it continually in the rear; he felt its necessity to any account of the human understanding that could be satisfactory to one who had meditated on Locke's theory as probed and searched by Leibnitz.

The Uncollected Writings of Thomas de Quincey—Vol. 1 With a Preface and Annotations by James Hogg Thomas De Quincey 1822