"Not that I at all disallow the use of reasoning upon experiments, or the endeavouring to discern as early as we can the confederations, and differences, and tendencies of things: for such an absolute suspension of the exercise of reasoning were exceeding troublesome, if not impossible. And, as in that rule of arithmetic, which is commonly called by proceeding upon a conjecturally-supposed number, as if it were that, which we inquire after, we are wont to come to the knowledge of the true number sought for; so in physiology it is sometimes conducive to the discovery of truth, to permit the understanding to make an hypothesis, in order to the explication of this or that difficulty, that by examining how far the phænomena are, or are not, capable of being solved by that hypothesis, the understanding may, even by its own errors, be instructed."

“But though much may be said to Excuse the Chymists when they write Darkly, and Ænigmatically, about the Preparation of their Elixir, and Some few other grand Arcana, the divulging of which they may upon Grounds Plausible enough esteem unfit; yet when they pretend to teach the General Principles of Natural Philosophers, this Equivocall Way of Writing is not to be endur'd. For in such Speculative Enquiries, where the naked Knowledge of the Truth is the thing Principally aim'd at, what does he teach me worth thanks that does not, if he can, make his Notion intelligible to me, but by Mystical Termes, and Ambiguous Phrases darkens what he should clear up; and makes me add the Trouble of guessing at the sence of what he Equivocally expresses, to that of examining the Truth of what he seems to deliver.”

“And if the matter of the Philosophers Stone, and the manner of preparing it, be such Mysteries as they would have the World believe them, they may Write Intelligibly and Clearly of the Principles of mixt Bodies in General, without Discovering what they call the Great Work.”

“The phaenomena afforded by trades, are a part of the history of nature, and therefore may both challenge the naturalist's curiosity and add to his knowledge, Nor will it suffice to justify learned men in the neglect and contempt of this part of natural history, that the men, from whom it must be learned, are illiterate mechanicks... is indeed childish, and too unworthy of a philosopher, to be worthy of an honest answer.”

“I fear that the chief Reason why Chymists have written so obscurely of their three Principles, may be, That not having Clear and Distinct Notions of them themselves, they cannot write otherwise then Confusedly of what they but Confusedly Apprehend. Not to say that divers of them, being Conscious to the Invalidity of their Doctrine, might well enough discerne that they could scarce keep themselves from being confuted, but by keeping themselves from being clearly understood.”

“I must confess I have, in the reading of Paracelsus and other Chymical Authors, been troubled to find, that such hard Words and Equivocal Expressions, as You justly complain of, do even when they treat of Principles, seem to be studiously affected by those Writers; whether to make themselves to be admir'd by their Readers, and their Art appear more Venerable and Mysterious, or, to conceal from them a Knowledge themselves judge inestimable.”

“I am glad to see the Vanity or Envy of the canting Chymists thus discover'd and chastis'd; and I could wish, that Learned Men would conspire together to make these deluding Writers sensible, that they must no longe hope with Impunity to abuse the World. For whilst such Men are quietly permitted to publish Books with promising Titles, and therein to Assert what they please, and contradict others, and ev'n themselves as they please, with as little danger of being confuted as of being understood, they are encourag'd to get themselves a name, at the cost of the Readers, by finding that intelligent Men are wont for the reason newly mention'd, to let their Books and Them alone: And the ignorant and credulous are forward to admire most what they least understand.”