For I am confident, if any confidence of a writing can proceed from the writer's fear, circumspection, and diffidence, that in the three former parts of this book all that I have said is sufficiently demonstrated from definitions; and all in the fourth part from suppositions not absurd. But if there appear to your Lordship anything less fully demonstrated than to satisfy every reader, the cause was this, that I professed to write not all to all, but some things to geometricians only. But that your Lordship will be satisfied, I cannot doubt. There remains the second section, which is concerning _Man_. That part thereof, where I handle the _Optics_, containing six chapters, together with the tables of the figures belonging to them, I have already written and engraven lying by me above these six years. The rest shall, as soon as I can, be added to it; though by the contumelies and petty injuries of some unskilful men, I know already, by experience, how much greater thanks will be due than paid me, for telling men the truth of what men are. But the burthen I have taken on me I mean to carry through; not striving to appease, but rather to revenge myself of envy, by encreasing it. For it contents me that I have your Lordship's favour, which, being all you require, I acknowledge; and for which, with my prayers to Almighty God for your Lordship's safety, I shall, to my power, be always thankful. Your Lordship's most humble servant, THOMAS HOBBES. London, April 23, 1655. THE AUTHOR'S EPISTLE TO THE READER.