do consider both my sex and breeding; for which favour and justice, I shall always remain, _Your most obliged Servant,_ M. N. Philosophical Letters. Sect. I. I. _MADAM,_ You have been pleased to send me the Works of four Famous and Learned Authors, to wit, of two most Famous Philosophers of our Age, _Des Cartes_, and _Hobbs_, and of that Learned Philosopher and Divine Dr. _More_, as also of that Famous Physician and Chymist _Van Helmont_. Which Works you have sent me not onely to peruse, but also to give my judgment of them, and to send you word by the usual way of our Correspondence, which is by Letters, how far, and wherein I do dissent from these Famous Authors, their Opinions in _Natural Philosophy_. To tell you truly, _Madam_, your Commands did at first much affright me, for it did appear, as if you had commanded me to get upon a high Rock, and fling my self into the Sea, where neither a Ship, nor a Plank, nor any kind of help was near to rescue me, and save my life; but that I was forced to sink, by reason I cannot swim: So I having no Learning nor Art to assist me in this dangerous undertaking, thought, I must of necessity perish under the rough censures of my Readers, and be not onely accounted a fool for my labour, but a vain and presumptuous person, to undertake things surpassing the ability of my performance; but on the other side I considered first, that those Worthy Authors, were they my censurers, would not deny me the same liberty they take themselves; which is, that I may dissent from their Opinions, as well as they dissent from others, and from amongst themselves: And if I should express more Vanity then Wit, more Ignorance then Knowledg, more Folly then Discretion, it being according to the Nature of our Sex, I hoped that my Masculine Readers would civilly excuse me, and my Female Readers could not justly condemn me. Next I considered with my self, that it would be a great advantage for my Book called _Philosophical Opinions_, as to make it more perspicuous and intelligible by the opposition of other Opinions, since two opposite things placed near each other, are the better discerned; for I must confess, that when I did put forth my Philosophical Work at first, I was not so well skilled in the Terms or Expressions usual in _Natural Philosophy_; and therefore for want of their knowledg, I could not declare my meaning so plainly and clearly as I ought to have done, which may be a sufficient argument to my Readers, that I have not read heretofore any _Natural Philosophers_, and taken some Light from them; but that my Opinions did meerly issue from the Fountain of my own Brain, without any other help or assistance. Wherefore since for want of proper Expressions, my named Book of _Philosophy_ was accused of obscurity and intricacy, I thought your Commands would be a means to explain and clear it the better, although not by an Artificial way, as by Logical Arguments or