The great physiologist Müller and the great philosopher Hegel are quoted by Mr. Mivart as maintaining, that “to form abstract conceptions of such operations as of something common to many under the notion of cause and effect, is a perfect impossibility to them” (animals[49]); and no doubt many other illustrious names might be quoted in support of the same statement. But it seems to me that needless obscurity is imported into this matter, by not considering in what our own idea of causality consists. It is clear that to attain a _general_ idea of causality as universal, &c., demands higher powers of abstract thought than are possessed by any animals, or even by the great majority of men; but it is no less clear that all men and most animals have a _generic_ idea of causality, in the sense of expecting uniform experience under uniform conditions. A cat sees a man knock at the knocker of a door, and observes that the door is afterwards opened: remembering this, when she herself wants to get in at that door, she jumps at the knocker, and waits for the door to be opened.[50] Now, can it be denied that in this act of inference, or imitation, or whatever name we choose to call it, the cat perceives such an association between the knocking and the opening as to feel that the former as antecedent was in some way required to determine the latter as consequent? And what is this but such a perception of causal relation as is shown by a child who blows upon a watch to open the case—thinking this to be the cause of the opening from the uniform deception practised by its parent,—or of the savage who plants nails and gunpowder to make them grow? And endless illustrations of such a perception of causality might be drawn from the everyday life of civilized man: indeed, how seldom does any one of us wait to construct a general proposition about causality in the abstract before we act on our practical knowledge of it. And that this practical knowledge in the case of animals enables them to form a generic idea, or recept, of the _equivalency_ between causes and effects—such that a perceived equivalency is recognized by them as an _explanation_—would appear to be rendered evident by the following fact, which I carefully observed for the express purpose of testing the question. I quote the incident from an already-published lecture, which was given before the British Association at Dublin, in 1878. “I had a setter dog which was greatly afraid of thunder. One day a number of apples were being shot upon the wooden floor of an apple-room, and, as each bag of apples was shot, it produced through the rest of the house a noise resembling that of distant thunder. My dog became terror-stricken at the sound; but as soon as I brought him to the apple-room and showed him the true _cause_ of the noise, he became again buoyant and cheerful as usual.”[51]