And therefore I think you have done very wisely to make it your business to consider the Phœnomena relating to the present question, which have been … - Robert Boyle

[T]hat which I am now entering upon being the Consideration of the things themselves whereinto Spagyrists resolve mixt Bodies by the Fire, If I can shew that these are not of an Elementary Nature, it will be no great matter what names these or those Chymists have been pleased to give them. And I question not that to a Wise man, and consequently to Eleutherius, it will be lesse considerable to know, what Men Have thought of Things, then what they Should have thought.

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.

Now a man need not be very conversant in the writings of Chymists to observe, in how Laxe, Indefinite, and almost Arbitrary Senses they employ the Terms of Salt, Sulphur and Mercury; of which I could never find that they were agreed upon any certain Definitions or setled Notions; not onely differing Authors, but not unfrequently one and the same, and perhaps in the same Book, employing them in very differing senses.