Bruno here asks the question: “But this first universal form and that first universal matter, how are they united, inseparable? Different—and yet one Being?” He answers by making use of the Aristotelian forms of δύναμις and ἐνέργεια: Matter is to be regarded as potentiality; in this way all possible forms of existence in a certain sense are included in the Notion of it. The passivity of matter must be regarded as pure and absolute. Now it is impossible to attribute existence to a thing which lacks the power to exist. Existence has, however, such an express reference to the active mode, that it is at once clear that the one cannot exist without the other, but that each of them presupposes the other. If therefore at all times a capacity of working, producing, creating, was there, so must there also have been at all times a capacity of being worked upon, produced, created. The perfect potentiality of the existence of things (matter) cannot precede their actual existence, and just as little can it remain after that is past. The first and most perfect principle includes all existence in itself, can be all things, and is all things. Active power and potentiality, possibility and actuality are therefore in it one undivided and indivisible principle.[77] This simultaneousness of acting and being acted upon is a very important determination; matter is nothing without activity, form is therefore the power and inward life of matter. If matter were nothing but indeterminate potentiality, how would the determinate be arrived at? This simplicity of matter is itself only one moment of form: in wishing therefore to tear asunder matter and form, matter is at once established in one determination of form, but in so doing there is immediately established also the existence of the Other. Thus the Absolute is determined for Bruno: it is not so with other things, which may exist and also may not exist, and which may be determined in one way or in another way. In regard to finite things and in finite determinations of the understanding the distinction between form and matter is thus present. The individual man is at every moment what he may be at that moment, but not everything which he may be in general and with reference to substance. The things which appear to be different are only modifications of one single thing which includes in its existence all other existence. The universe, unbegotten Nature, is, however, everything which it can be in reality and at one time, because it includes in itself the whole of matter, as well as the eternal, unchangeable form of its changing forms. But in its developments from moment to moment, its particular parts, qualities, individual existences, in its externality as a whole, it is no more what it is and may be; but a part such as this is only a shadow of the image of the first principle.[78] Thus Bruno wrote also a book, _De umbris idearum_.