But the old natural philosophers, who had no notion of primitive unextended elements, when affirming the eduction of substantial forms out of the potency of matter, took for granted that such forms were strictly substantial, and gave the first being not only to the body, but also to the matter itself of which the body was composed. In this they were mistaken; but the mistake was excusable, as chemistry had not yet shown the law of definite proportions in the combination of different bodies, nor had the spectroscope revealed the fact that the primitive molecules of all bodies are composed of free elementary substances vibrating around a common centre, and remaining substantially identical amid all the changes produced by natural causes in the material world. Nevertheless, had they not been biassed by the _Ipse dixit_, the peripatetics would have found that, though accidental forms, and many essential forms too, are educed out of the potency of matter, yet the strictly substantial forms cannot be so educed. The matter may be conceived either as formed or as unformed. If it is formed, it is already in possession of its substantial form and of its first being, which it never loses, as we shall prove hereafter. Therefore such a matter is not in potency with regard to its first being; and thus no strictly substantial form can be educed from the potency of the formed matter. If, on the contrary, the matter is yet unformed, it is plain that such a matter cannot be acted on by natural agents; for it has no existence in the order of things, and therefore it cannot be the subject of natural actions. How, then, can it receive the first being? Owing to the impossibility of explaining how the unformed matter could be actuated by natural agents, those who admitted the eduction of substantial forms out of the potency of matter were constrained to assume that the _first_ matter had some reality of its own, and consisted intrinsically, as Suarez teaches, of act and potency. But, though it is true that the matter must have some reality in order to receive from natural agents a new form, it is evident that such a new form cannot be strictly substantial; for it cannot give the first being to a matter already endowed with being. Hence no strictly substantial form can be naturally educed out of the potency of matter.