And your _Sennertus_ Himself (though an Author I much value) would I fear have been exceedingly puzl'd to resolve, by the _Tria Prima_, halfe that Catalogue of Problems, which he challenges the Vulgar Peripateticks to explicate by their four Elements.[26] And supposing it were true, that Salt or Sulphur were the Principle to which this or that Quality may be peculiarly referr'd, yet though he that teaches us this teaches us something concerning That quality, yet he Teaches us but something. For indeed he does not Teach us That which can in any Tollerable measure satisfie an inquisitive Searcher after Truth. For what is it to me to know, that such a quality resides in such a Principle or Element, whilst I remain altogether ignorant of the Cause of that quality, and the manner of its production and Operation? How little do I know more then any Ordinary Man of Gravity, if I know but that the Heaviness of mixt bodies proceeds from that of the Earth they are compos'd of, if I know not the reason why the Earth is Heavy? And how little does the Chymist teach the Philosopher of the Nature of Purgatition, if he only tells him that the Purgative Vertue of Medicines resides in their Salt? For, besides that this must not be conceded without Limitation, since the purging parts of many Vegetables Extracted by the Water wherein they are infus'd, are at most but such compounded Salts, (I mean mingl'd with Oyle, and Spirit, and Earth, as Tartar and divers other Subjects of the Vegetable Kingdom afford;) And since too that Quicksilver precipitated either with Gold, or without Addition, into a powder, is wont to be strongly enough Cathartical, though the Chymists have not yet prov'd, that either Gold or Mercury have any Salt at all, much less any that is Purgative; Besides this, I say, how little is it to me, to know That 'tis the Salt of the Rhubarb (for Instance) that purges, if I find That it does not purge as Salt; since scarce any Elementary Salt is in small quantity cathartical. And if I know not how Purgation in general is effected in a Humane Body? In a word, as 'tis one thing to know a mans Lodging, and another, to be acquainted with him; so it may be one thing to know the subject wherein a Quality principally resides, and another thing to have a right notion and knowledg of the quality its self. Now that which I take to be the reason of this Chymical Deficiency, is the same upon whose account I think the _Aristotelian_ and divers other Theories incompetent to explicate the Origen [Errata: origine] of Qualities. For I am apt to think, that men will never be able to explain the _Phaenomena_ of Nature, while they endeavour to deduce them only from the Presence and Proportion of such or such material Ingredients, and consider such ingredients or Elements as Bodies in a state of rest; whereas indeed the greatest part of the affections of matter, and consequently of the _Phaenomena_ of nature, seems to depend upon the motion and the