But if judicious men skilled in Chymical affairs shall once agree to write clearly and plainly of them, and thereby keep men from being stunn'd... or… - Robert Boyle

I find that even Eminent Writers (such as Raymund Lully, Paracelsus, and others) do so abuse the termes they employ, that as they will now and then give divers things one name, so they will oftentimes give one thing, many Names; and some of them (perhaps) such, as do much more properly signifie some Distinct Body of another kind; nay even in Technical Words or Termes of Art, they refrain not from this Confounding Liberty; but will, as I have Observ'd call the same Substance, sometimes the Sulphur, and Sometimes the Mercury, of a Body.

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.

I observe, that of late Chymistry begins, as indeed it deserves, to be cultivated by Learned Men who before despis’d it; and to be pretended to by many who never cultivated it, that they may be thought not to ignore it: Whence it is come to passe, that divers Chymical Notions about Matters Philosophical are taken for granted and employ’d, and so adopted by very eminent Writers both Naturalists and Physitians. Now this I fear may prove somewhat prejudicial to the Advancement of solid Philosophy: For though I am a great Lover of Chymical Experiments, and though I have no mean esteem of divers Chymical Remedies, yet I distinguish these from their Notions about the causes of things, and their manner of Generation.