Aristotle characterizes the nature of the soul more closely (De Anima, II. 1) by referring to the three moments of existence: “First there is matter (ὕλη), which is in itself no individual thing; secondly, the form and the universal (μορφὴ καὶ εἶδος), which give a thing individuality; thirdly, the result produced by both, in which matter is potentiality and form is energy (ἐντελέχεια);” matter thus does not exist as matter, but only implicitly. “The soul is substance, as being the form of the physical organic body which is possessed potentially of life; but its substance is energy (ἐντελέχεια), the energy of a body such as has been described” (endowed with life). “This energy appears in twofold form: either as knowledge (ἐπιστήμη) or as active observation (τὸ θεωρεῖν). But it is evident that here it is to be regarded as the former of these. For the soul is present with us both when we sleep and when we wake; waking corresponds with active observation, and sleep with possession and passivity. But knowledge is in origination prior to all else. The soul is thus the first energy of a physical but organic body.” It is in respect of this that Aristotle gives to the soul the definition of being the entelechy (_supra_, pp. 143, 144). In the same chapter Aristotle comes to the question of the mutual relation of body and soul. “For this reason” (because soul is form) “we must no more ask if soul and body are one than we ask if wax and its form are one, or, in general, if matter and its forms are one. For though unity and Being are used in various senses. Being is essentially energy.” Were we, namely, to pronounce body and soul one in the same way that a house, which consists of a number of parts, or as a thing and its properties, or the subject and predicate, and so on, are called one, where both are regarded as things, materialism results. An identity such as this is an altogether abstract, and therefore a superficial and empty determination, and a term which it is a mistake to employ, for form and material do not rank equally as regards Being; identity truly worthy of the name is to be apprehended as nothing else than energy such as has been described. The only question that now arises is whether activity and the organ it employs are one; and our idea is to answer in the affirmative. The more definite explanation of this relation is to be found in the following; “The soul is substance, but only according to the Notion (κατὰ τὸν λόγον); but that is the substantial form (τὸ τί ἦν εἶναι)[96] for such and such a body. For suppose that an instrument, such as an axe, were a natural body, this form, this axehood, would be its substance, and this its form would be its soul, for if this were to be taken away from it, it would no longer be an axe, the name only would remain. But soul is not the substantial form and Notion of such a body as an axe, but of a body which has within itself the principle of movement and of rest.” The axe has not