In all these instances the fact which was dignified by the name of cause, was the one condition which came last into existence. But it must not be supposed that in the employment of the term this or any other rule is always adhered to. Nothing can better shew the absence of any scientific ground for the distinction between the cause of a phenomenon and its conditions, than the capricious manner in which we select from among the conditions that which we choose to denominate the cause. However numerous the conditions may be, there is hardly any of them which may not, according to the purpose of our immediate discourse, obtain that nominal pre-eminence. This will be seen by analysing the conditions of some one familiar phenomenon. For example, a stone thrown into water falls to the bottom. What are the conditions of this event? In the first place there must be a stone, and water, and the stone must be thrown into the water; but, these suppositions forming part of the enunciation of the phenomenon itself, to include them also among the conditions would be a vicious tautology, and this class of conditions, therefore, have never received the name of cause from any but the schoolmen, by whom they were called the _material_ cause, _causa materialis_. The next condition is, there must be an earth: and accordingly it is often said, that the fall of a stone is caused by the earth; or by a power or property of the earth, or a force exerted by the earth, all of which are merely roundabout ways of saying that it is caused by the earth; or, lastly, the earth’s attraction; which also is only a technical mode of saying that the earth causes the motion, with the additional particularity that the motion is _towards_ the earth, which is not a character of the cause, but of the effect. Let us now pass to another condition. It is not enough that the earth should exist; the body must be within that distance from it, in which the earth’s attraction preponderates over that of any other body. Accordingly we may say, and the expression would be confessedly correct, that the cause of the stone’s falling is its being _within the sphere_ of the earth’s attraction. We proceed to a further condition. The stone is immersed in water: it is therefore a condition of its reaching the ground, that its specific gravity exceed that of the surrounding fluid, or in other words that it surpass in weight an equal volume of water. Accordingly any one would be acknowledged to speak correctly who said, that the cause of the stone’s going to the bottom is its exceeding in specific gravity the fluid in which it is immersed.