Of this work, to which all my other writings (unless I except my Poems, and these I can exclude in part only) are introductory and preparative; and the result of which (if the premises be, as I with the most tranquil assurance, am convinced they are--insubvertible, the deductions legitimate, and the conclusions commensurate, and only commensurate, with both), must finally be a revolution of all that has been called _Philosophy_ or Metaphysics in England and France since the era of the commencing predominance of the mechanical system at the restoration of our second Charles, and with this the present fashionable views, not only of religion, morals, and politics, but even of the modern physics and physiology. You will not blame the earnestness of my expressions, nor the high importance which I attach to this work; for how, with less noble objects, and less faith in their attainment, could I stand acquitted of folly, and abuse of time, talents, and learning, in a labour of three-fourths of my _intellectual_ life? Of this work, something more than a volume has been dictated by me, so as to exist fit for the press, to my friend and enlightened pupil, Mr. Green; and more than as much again would have been evolved and delivered to paper, but that, for the last six or eight months, I have been compelled to break off our weekly meeting, from the necessity of writing (alas! alas! of _attempting_ to write) for purposes, and on the subjects of the passing day.--Of my poetic works, I would fain finish the _Christabel_. Alas! for the proud time when I planned, when I had present to my mind, the materials, as well as the scheme, of the Hymns entitled _Spirit_, _Sun_, _Earth_, _Air_, _Water_, _Fire_, and _Man_: and the Epic Poem on--what still appears to me the one only fit subject remaining for an Epic Poem--_Jerusalem besieged and destroyed by Titus_.