conference betwixt Carneades and Eleutherius, as to some other Dialogues, which for certain reasons are not now herewith publish’d, I resolv’d to supply, as well as I could, the Contents of a Paper belonging to the second of the following Discourses, which I could not possibly retrive, though it were the chief of them all. And having once more try’d the Opinion of Friends, but not of the same, about this imperfect work, I found it such, that I was content in complyance with their Desires; that not only it should be publish’d, but that it should be publish’d as soon as conveniently might be. I had indeed all along the Dialogues spoken of my self, as of a third Person; For, they containing Discourses which were among the first Treatises that I ventur’d long ago to write of matters Philosophical, I had reason to desire, with the Painter, to latere pone tabulam, and hear what men would say of them, before I own’d my self to be their Author. But besides that now I find, ’tis not unknown to many who it is that writ them, I am made to believe that ’tis not inexpedient, they should be known to come from a Person not altogether a stranger to Chymical Affairs. And I made the lesse scruple to let them come abroad uncompleated, partly, because my affairs and Præ-ingagements to publish divers other Treatises allow’d me small hopes of being able in a great while to compleat these Dialogues. And partly, because I am not unapt to think, that they may come abroad seasonably enough, though not for the Authors reputation, yet for other purposes. For 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. And for ought I can hitherto discern, there are a thousand Phænomena in Nature, besides a Multitude of Accidents relating to the humane Body, which will scarcely be clearly & satisfactorily made out by them that confine themselves to deduce things from Salt, Sulphur and Mercury, and the other Notions peculiar to the Chymists, without taking much more Notice than they are wont to do, of the Motions and Figures, of the small Parts of Matter, and the other more Catholick and Fruitful affections of Bodies. Wherefore it will not perhaps be now unseasonable to let our Carneades warne Men, not to subscribe to the grand Doctrine of the Chymists touching their three Hypostatical Principles, till they have a little examin’d it, and consider’d, how they can clear it from his Objections, divers of which ’tis like they may never have thought on; since a Chymist scarce would, and none but a Chymist could propose them. I hope also it will not be unacceptable to several Ingenious Persons, who are unwilling to determine of any important Controversie, without a previous consideration of what may be said on both sides, and yet have greater desires to understand Chymical Matters, than Opportunities of learning them, to find here together, besides several Experiments of my own purposely made to Illustrate the Doctrine of the Elements, divers others scarce to be met with, otherwise then Scatter’d among many Chymical Books. And to Find these Associated Experiments so Deliver’d as that an Ordinary Reader, if he be but Acquainted with the usuall Chymical Termes, may easily enough Understand Them; and even a wary One may safely rely on Them. These Things I add, because a Person any Thing vers’d in the Writings of Chymists cannot but Discern by their obscure, Ambiguous, and almost Ænigmatical Way of expressing what they pretend to Teach, that they have no Mind, to be understood at all, but by the Sons of Art (as they call them) nor to be Understood even by these without Difficulty And Hazardous Tryalls. Insomuch that some of Them Scarce ever speak so candidly, as when they make use of that known Chymical Sentence; Ubi palam locuti fumus, ibi nihil diximus. And as the obscurity of what some Writers deliver makes it very difficult to be understood; so the Unfaithfulness of too many others makes it unfit to be reli’d on. For though unwillingly, Yet I must for the truths sake, and the Readers, warne him not to be forward to believe Chymical Experiments when they are set down only by way of Prescriptions, and not of Relations; that is, unless he that delivers them mentions his doing it upon his own particular knowledge, or upon the Relation of some credible person, avowing it upon his own experience. For I am troubled, I must complain, that even Eminent Writers, both Physitians and Philosophers, whom I can easily name, if it be requir’d, have of late suffer’d themselves to be so far impos’d upon, as to Publish and Build upon Chymical Experiments, which questionless they never try’d; for if they had, they would, as well as I, have found them not to be true. And indeed it were to be wish’d, that now that those begin to quote Chymical Experiments that are not themselves Acquainted with Chymical Operations, men would Leave off that Indefinite Way of Vouching the Chymists say this, or the Chymists affirme that, and would rather for each Experiment they alledge name the Author or Authors, upon whose credit they relate it; For, by this means they would secure themselves from the suspition of falshood (to which the other Practice Exposes them) and they would Leave the Reader to Judge of what is fit for him to Believe of what is Deliver’d, whilst they employ not their own great names to Countenance doubtfull Relations; and they will also do Justice to the Inventors or Publishers of true Experiments, as well as upon the Obtruders of false ones. Whereas by that general Way of quoting the Chymists, the candid Writer is Defrauded of the particular Praise, and the Impostor escapes the Personal Disgrace that is due to him.

The remaining Part of this Præface must be imploy’d in saying something for Carneades, and something for my Self.

And first, Carneades hopes that he will be thought to have disputed civilly and Modestly enough for one that was to play the Antagonist and the Sceptick. And if he any where seem to sleight his Adversaries Tenents and Arguments, he is willing to have it look’d upon as what he was induc’d to, not so much by his Opinion of them, as the Examples of Themistius and Philoponus, and the custom of such kind of Disputes.

Next, In case that some of his Arguments shall not be thought of the most Cogent sort that may be, he hopes it will be consider’d that it ought not to be Expected, that they should be So. For, his Part being chiefly but to propose Doubts and Scruples, he does enough, if he shews that his Adversaries Arguments are not strongly Concluding, though his own be not so neither. And if there should appear any disagreement betwixt the things he delivers in divers passages, he hopes it will be consider’d, that it is not necessary that all the things a Sceptick Proposes, should be consonant; since it being his work to Suggest doubts against the Opinion he questions, it is allowable for him to propose two or more severall Hypotheses about the same thing: And to say that it may be accounted for this way, or that way, or the other Way, though these wayes be perhaps inconsistent among Themselves. Because it is enough for him, if either of the proposed Hypotheses be but as probable as that he calls a question. And if he proposes many that are Each of them probable, he does the more satisfie his doubts, by making it appear the more