Page:Reflections upon ancient and modern learning (IA b3032449x).pdf/283

 The Natural History of Earth and Water come under that of Minerals: Fire, as it appears to our Senses, seems to be a Quality, rather than a Substance; and to consist in its own Nature, in a Rapid Agitation of Bodies, put into a quick Motion; and divided by this Motion, into very small Parts. After this had been once asserted by the Corpuscularian Philosophers, it was exceedingly strengthned [sic] by many Experimental Writers, who have taken abundance of Pains to state the whole Doctrine of Qualities clearly, and intelligibly; that so Men might know the difference between the Existence or Essential Nature of a Body, and its being represented to our Senses under such or such an Idea. This is the Natural Consequence of proceeding upon clear and intelligible Principles; and resolving to admit nothing as conclusive, which cannot be manifestly conceived, and evidently distinguished from every Thing else. Here, if in any Thing, the old Philosophers were egregiously defective: What has been done since, will appear by consulting, among others, the Discourses which Mr. Boyle has written upon most of the considerable Qualities of Bodies, which come under our Notice; such as his Histories of Fluidity and