| The idea, then, of causation must be derived from some relation among objects; and that relation we must now endeavour to discover. |
| I find in the first place, that whatever objects are considered as causes or effects, are contiguous; and that nothing can operate in a time or place, which is ever so little removed from those of its existence. |
| Though distant objects may sometimes seem productive of each other, they are commonly found upon examination to be linked by a chain of causes, which are contiguous among themselves, and to the distant objects; and when in any particular instance we cannot discover this connexion, we still presume it to exist. |
| We may therefore consider the relation of CONTIGUITY as essential to that of causation; at least may suppose it such, according to the general opinion, till we can find a more [Part IV. SECT. 5.] proper occasion to clear up this matter, by examining what objects are or are not susceptible of juxtaposition and conjunction. |
| The second relation I shall observe as essential to causes and effects, is not so universally acknowledged, but is liable to some controversy. |
| It is that of PRIORITY Of time in the cause before the effect. |
| Some pretend that it is not absolutely necessary a cause should precede its effect; but that any object or action, in the very first moment of its existence, may exert its productive quality, and give rise to another object or action, perfectly co-temporary with itself. |
| But beside that experience in most instances seems to contradict this opinion, we may establish the relation of priority by a kind of inference or reasoning. |
| It is an established maxim both in natural and moral philosophy, that an object, which exists for any time in its full perfection without producing another, is not its sole cause; but is assisted by some other principle, which pushes it from its state of inactivity, and makes it exert that energy, of which it was secretly possest. |
| Now if any cause may be perfectly co-temporary with its effect, it is certain, according to this maxim, that they must all of them be so; since any one of them, which retards its operation for a single moment, exerts not itself at that very individual time, in which it might have operated; and therefore is no proper cause. |
| The consequence of this would be no less than the destruction of that succession of causes, which we observe in the world; and indeed, the utter annihilation of time. |
| For if one cause were co-temporary with its effect, and this effect with its effect, and so on, it is plain there would be no such thing as succession, and all objects must be co-existent. |
| If this argument appear satisfactory, it is well. |
| If not, I beg the reader to allow me the same liberty, which I have used in the preceding case, of supposing it such. |
| For he shall find, that the affair is of no great importance. |
| Having thus discovered or supposed the two relations of contiguity and succession to be essential to causes and effects, I find I am stopt short, and can proceed no farther in considering any single instance of cause and effect. |
| Motion in one body is regarded upon impulse as the cause of motion in another. |
| When we consider these objects with utmost attention, we find only that the one body approaches the other; and that the motion of it precedes that of the other, but without any, sensible interval. |
| It is in vain to rack ourselves with farther thought and reflection upon this subject. |
| We can go no farther in considering this particular instance. |
| Should any one leave this instance, and pretend to define a cause, by saying it is something productive of another, it is evident he would say nothing. |