XIII. It is not my intention, to examine the nature and origin of all, or either of these qualities; but shall only say, that they are all equally occult, or are all equally manifest. In order to demonstrate this, we will compare the calefactive virtue of fire which is looked upon as the most manifest, with the attractive virtue of the load-stone, which is reputed the most occult. All that is known, or that is taught by the peripatetic doctrine, of the calefactory virtues of fire, may be reduced to this, that it is a property appertaining to that substance, or a quality that springs from, or arises out of its form, that produces the effect which we call heat, and that the action with which it causes it, is called calefaction; but so it is, that it is just in the same manner that we know the attractive virtue of the load-stone; _viz._ that it is a property or quality, springing from, or arising out of the form of this entity, that produces the sensible effect of drawing the iron to it, and that the action with which it causes it to approach towards it, is called attraction; it follows then, that we know just as much of the attractive virtue of the load-stone, as we know of the calefactory virtues of fire; and therefore, both of them are equally occult, and equally manifest. XIV. And if we were to speak the truth, how could we deny, that the quality we call heat is occult, when it is even occult, whether it is or is not a quality? Not only the corpuscular philosophers deny it to be possessed of all quality or form, but many of those who admit those properties to be contained in it, constitute the heat to proceed from a vertical, or vibratory motion of the insensible particles of the body. And so long as we shall remain without an argument to convince us of the truth of these opinions, we shall not know which of them is right. PARADOX V. _It is false, in a general and comprehensive sense, that Virtue by being united becomes the stronger._ SECT. V.