With the first class of ideas, _i.e._, the real world of perception, the idea of matter is also given; because the law governing this class of ideas, the law of causality, determines the change of the states or conditions, and these conditions themselves presuppose something permanent, whose changes they are. When speaking above of the principle of the permanence of substance, I showed, by reference to earlier passages, that this idea of matter arises because in the understanding, for which alone it exists, time and space are intimately united, and the share of space in this product exhibits itself as the permanence of matter, while the share of time appears as the change of states. Purely in itself, matter can only be thought _in abstracto_, and not perceived; for to perception it always appears already in form and quality. From this conception of _matter_, _substance_ is again an abstraction, consequently a higher _genus_, and arose in this way. Of the conception of matter, only the predicate of permanence was allowed to remain, while all its other essential properties, extension, impenetrability, divisibility, &c., were thought away. Like every higher _genus_, then, the concept _substance_ contains _less in itself_ than the concept _matter_, but, unlike every other higher _genus_, it does not contain _more under it_, because it does not include several lower _genera_ besides matter; but this remains the one true species of the concept substance, the only assignable thing by which its content is realised and receives a proof. Thus the aim with which in other cases the reason produces by abstraction a higher conception, in order that in it several subordinate species may be thought at once through common determinations, has here no place; consequently that abstraction is either undertaken idly and entirely without aim, or it has a secret secondary purpose. This secret purpose is now brought to light; for under the conception substance, along with its true sub-species matter, a second species is co-ordinated—the immaterial, simple, indestructible substance, soul. But the surreptitious introduction of this last concept arose from the fact that the higher concept _substance_ was framed illogically, and in a manner contrary to law. In its legitimate procedure the reason always frames the concept of a higher genus by placing together the concepts of several species, and now comparing them, proceeds discursively, and by omitting their differences and retaining the qualities in which they agree, obtains the generic concept which includes them all but has a smaller content. From this it follows that the concepts of the species must always precede the concept of the genus. But, in the present case, the converse is true. Only the concept matter existed before the generic concept _substance_. The latter was without occasion, and consequently without justification, as it were aimlessly framed from the