22 



cumstance is distingnished from all associations ; a distinction, how- 

 ever, which it it is sometimes most difficult to make, but which, for 

 the purpose of accurate reasoning, is of all other distinctions the 

 most essential. 



30. The test of a mere connection is the abstraction of the 

 thing, or property, constituting perhaps a supposed cause, and the 

 permanence or cessation of the effect. If, upon the removal of a 

 connected substance, the effect remains unchanged, the substance in 

 question is an associated or connected one only, and no cause; and 

 the contrary. 



31. The relation between causes, disposing them to unite and 

 form effects, is sometimes called an affinity ; it is, however, an act 

 of causation produced by properties inherent, though seldom or 

 never perceived in the causes. This act has also its effect, which 

 is among the latent combinations of the causes of bodies. 



32. Thus we see that causes are identified with effects, that 

 there is no cause which is not contained in the effect, for a cause is 

 that without which the effect cannot exist. There are in the sciences 

 many instances which I could point out, and most likely a great 

 many more with which I am not in the least acquainted, where 

 associations are currently considered as causes. Indeed nobody has 

 been at the pains to define this matter, and it is therefore no won- 

 der that such a mistake should prevail. A person sees at a distance 

 a horse, and he is ready to affirm that the horse is the cause of this 

 instance of vision; but it is net so ; the cause which produces vision 

 in this case is, according to the common theory, the modification of 

 light; and the same vision (as by the shadowy representation of a 

 horse) may be produced by the same modification of light, where 

 there is no horse. Now this example would be urged as an ob- 

 jection to my principle; but examples should be scrutinized before 

 we give them an application. It will be said (pursuing the objec- 

 tion), the horse is the cause of the idea we have of a horse ; yet we 

 have this idea when the horse is not present: and certainly this 

 cause, viz. the horse, never entered into our minds, and became a 

 cause of the effect by existing in it, in the way described. Let us 

 follow this matter to the extremity. 



33. The mistake is this, that a whole series of processes of 

 causation is considered only as one act. The stomach and digestive 

 organs, the lungs, the heart, the blood, and the blood-vessels ; the 

 brain, the spinal marrow, and the nerves; the bones, the muscles, 

 the skin, and all other parts, and minutest constituents of the parts 

 of the animal, are the causes of the identity of the horse; by these 

 and by its life, it has certain properties of solidity, colour, figure, 

 &c.: these latter have a relation with light, that is, they conjoin 

 with it to produce an effect; while the internal viscera, all parts 

 beneath the surface, have no relation with light: light has a relation 

 with the eye and acts upon it, while of course the internal viscera, 

 not being concerned in this relation, are not comprised in the effects 

 of it. The cause of vision is the modification of light, producing a 



