I here refer the thoughtful reader to the explanations I have given in my chief work.[60] For it is of the highest importance that our conception of the true and proper meaning of the law of causality and the sphere of its validity should be perfectly clear and definite: before all things, that we should recognize, that this law refers solely and exclusively to _changes_ of material states and to nothing else whatever; consequently, that it ought not to be brought in when _these_ are not in question. The law of causality is the regulator of the _changes_ undergone in Time by objects of our outer _experience_; but these objects are all material. Each change can only be brought about by another having preceded it, which is determined by a rule, and then the new change takes place as being necessarily induced by the preceding one. This necessity is the causal nexus.
[60] "Die Welt a. W. u. V." vol. ii. chap. 4, especially p. 42 and _seq._ of the 2nd edition; p. 46 _seq._ of the 3rd edition.
However simple therefore the law of causality is, we nevertheless find it expressed quite differently in all philosophical manuals, from the earliest down to the latest ages: namely, in a broader, more abstract, therefore less definite way. We are, for instance, informed, now, that it is that by which something else comes into being; now, that it is what produces another thing or gives it reality, &c. &c. Wolf says: _Causa est principium, a quo existentia, sive actualitas, entis alterius dependet_; whereas it is obvious that in causality we have only to do with changes in the form of uncreated, indestructible Matter, and that a springing into existence of what did not previously exist is an impossibility. Want of clearness of thought may, no doubt, in most cases have led to these views of the causal relation; but surely sometimes an _arrière-pensée_ lurks in the background--a theological intention coqueting with the Cosmological Proof, for whose sake it is ready to falsify even transcendental, _à priori_ truths, the mother's milk of human understanding. We find the clearest instance of this in Thomas Brown's book, "On the Relation of Cause and Effect," a work of 460 pages, which, in 1835, had already reached its fourth edition, and has probably since gone through several more, and which, in spite of its wearisome, pedantic, rambling prolixity, does not handle the subject badly. Now this Englishman rightly recognises, that it is invariably with _changes_ that the causal law has to do, and that every effect is accordingly a _change_. Yet, although it can hardly have escaped him, he is unwilling to admit that every cause is likewise a _change_, and that the whole process is therefore nothing but the uninterrupted nexus of _changes_ succeeding one another in Time. On the contrary, he persists in clumsily calling the cause an _object_ or _substance_, which precedes the change, and in tormenting himself throughout his tedious book with this entirely false expression, which spoils all his explanations, notwithstanding his own better knowledge and against his conscience, simply in order that his definition may on no account stand in the way of the Cosmological Proof, which others might hereafter state elsewhere.--But what can a truth be worth which needs devices such as these to prepare its way?