Treatise III. In what way demonstration is in the several causes. Chapter I. That when something is demonstrated through a cause, the cause ought to be ordered in the middle.

TREATISE III. In what way demonstration is in the several causes. CHAPTER I. That when something is demonstrated through a cause, the cause ought to be ordered in the middle. In what was already had, determination has now been made concerning the middle, which is what it is, according to the way of cognition, that is, by what way it is known. But because what it is is also a cause, therefore one must touch upon the middle according as it is a cause; and this concerns that which is what insofar as it is on account of what. And therefore one must also touch upon the other causes. Therefore we say that, since we think that we know when we know the cause, here one must determine concerning the middle of demonstration according as it is a cause. But causes are four, of which one indeed is formal, which signifies what it was to be, and the definition according to form, which states the whole being. But one, that is, another or second, which is the material cause, is necessity as cause. And this is such that, when these things are, which bring matter to ultimate necessity, it is necessary that these things be, that is, the things caused by it, because otherwise matter cannot be posited in demonstrative matters in which the conclusion follows from necessity. For if matter were described according as it is in potency, it would not infer the conclusion from necessity; nor would matter be a cause even when disposed by the ultimate disposition to form, unless, because it has now received form, it necessarily infers the thing caused. But otherwise and in a third genus of causality, the moving or efficient cause is named, which moves toward the effect as to the first, that is, per se and formally. A fourth cause also is named, through whose middle all those causes are demonstrated, because that is the cause of causes, and is the final cause. But we said concerning the material cause that when this exists, it is necessary that there be something which is the effect. But this is not to be understood thus, that from one proposition it is necessary that something follow, if nevertheless one proposition is accepted, because from one thing nothing follows syllogistically; but when two propositions have been accepted, at least a conclusion follows syllogistically. But this occurs when two propositions have one middle, in which the extremes of those two propositions communicate. Therefore when this one middle has been accepted according as it unites the extremes, it is necessary that the conclusion be or follow. For here we intend to speak about causes according as they are a principle of cognition, namely a middle ¹. But according as they are related to the being and coming-to-be which they cause, it belongs to the second book of the Physics to determine concerning them; but in common, insofar as they are differences of being according as individual sciences consider these or those, to determine concerning them belongs to the fifth book of the First Philosophy. <marginal-label>Sufficiency of the four causes.</marginal-label> For there are four causes either of being or of coming-to-be. If of being, either it is formal, which gives being, or material, to which being is given. But if they are causes of coming-to-be, either it is the cause which begins the coming-to-be, and is efficient, or the cause which terminates the coming-to-be, and is final, because the motion of the efficient cause endures up to the ultimate included end, and then it rests.