Experiments wont to be alledg’d as Demonstrations of it, yet those I shall at present offer you may be conveniently enough comprehended in four Capital Considerations; touching all which I shall only premise this in general, That since it is not my present Task so much to assert an Hypothesis of my own, as to give an Account wherefore I suspect the Truth of that of the Chymists, it ought not to be expected that all my Objections should be of the most cogent sort, since it is reason enough to Doubt of a propos’d Opinion, that there appears no cogent Reason for it.
To come then to the Objections themselves; I consider in the first place, That notwithstanding what common Chymists have prov’d or taught, it may reasonably enough be Doubted, how far, and in what sence, Fire ought to be esteem’d the genuine and universal Instrument of analyzing mixt Bodies.
This Doubt, you may remember, was formerly mention’d, but so transiently discours’d of, that it will now be fit to insist upon it; And manifest that it was not so inconsiderately propos’d as our Adversaries then imagin’d.
