Wherefore, all propositions concerning future things, contingent or not contingent, as this, _it will rain tomorrow_, or this, _tomorrow the sun will rise_, are either necessarily true, or necessarily false; but we call them contingent, because we do not yet know whether they be true or false; whereas their verity depends not upon our knowledge, but upon the foregoing of their causes. But there are some, who though they confess this whole proposition, _tomorrow it will either rain, or not rain_, to be true, yet they will not acknowledge the parts of it, as, _tomorrow it will rain_, or, _tomorrow it will not rain_, to be either of them true by itself; because they say neither this nor that is true _determinately_. But what is this _determinately true_, but true upon our knowledge, or evidently true? And therefore they say no more but that it is not yet known whether it be true or no; but they say it more obscurely, and darken the evidence of the truth with the same words, with which they endeavour to hide their own ignorance. [Sidenote: Active power consists in motion.] 6. In the 9th article of the preceding chapter, I have shewn that the efficient cause of all motion and mutation consists in the motion of the agent, or agents; and in the first article of this chapter, that the power of the agent is the same thing with the efficient cause. From whence it may be understood, that all active power consists in motion also; and that power is not a certain accident, which differs from all acts, but is, indeed, an act, namely, motion, which is therefore called power, because another act shall be produced by it afterwards. For example, if of three bodies the first put forward the second, and this the third, the motion of the second, in respect of the first which produceth it, is the act of the second body; but, in respect of the third, it is the active power of the same second body. [Sidenote: Cause, formal and final, what they are.] 7. The writers of metaphysics reckon up two other causes besides the _efficient_ and _material_, namely, the ESSENCE, which some call the _formal cause_, and the END, or _final cause_; both which are nevertheless efficient causes. For when it is said the essence of a thing is the cause thereof, _as to be rational is the cause of man_, it is not intelligible; for it is all one, as if it were said, _to be a man is the cause of man_; which is not well said. And yet the knowledge of the _essence_ of anything, is the cause of the knowledge of the thing itself; for, if I first know that a thing is _rational_, I know from thence, that the same is _man_; but this is no other than an efficient cause. A _final cause_ has no place but in such things as have sense and will; and this also I shall prove hereafter to be an efficient cause. ------- CHAPTER XI. OF IDENTITY AND DIFFERENCE.