"To every form of organic structure this definition applies, for even the parts of plants are organs, although very simple ones; thus the outer leaf is a protection to the pericarp, and the pericarp to the fruit. Or, again, the roots are organs bearing an analogy to the mouth in animals, both serving to take in food. Putting our definition, then, into a form applicable to every stage of the Vital principle, we shall say that _The Soul is the earliest realisation of a natural body having organisation_. "In this way we are relieved from the necessity of asking whether Soul and body are one. We might as well ask whether the wax and the impression are one, or, in short, whether the _matter_ of any object and that whereof it is the matter or substratum are one. As has been pointed out, unity and substantiality may have several significations, but the truest sense of both is found in _realisation_. "The general definition of the Soul or Vital principle above given may be further explained as follows. The Soul is the _rational_ substance (or function), that is to say, it is that which gives essential meaning and reality to a body as knowable. Thus if an axe were a _natural_ instrument or organ, its rational substance would be found in its realisation of what an axe means; this would be its _soul_. Apart {206} from such realisation it would not be an axe at all, except in name. Being, however, such as it is, the axe remains an axe independently of any such realisation. For the statement that the Soul is the _reason_ of a thing, that which gives it essential meaning and reality, does not apply to such objects as an axe, but only to natural bodies having power of spontaneous motion (including growth) and rest.