David Hume

“ Having thus discover'd or suppos'd 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 the utmost attention, we find only that the one body approaches the other ”

“ These three relations are identity, the situations in time and place, and causation.
All kinds of reasoning consist in nothing but a companion, and a discovery of those relations, either constant or inconstant, which two or more objects bear to each other. This comparison we may make, either when both the objects are present to the senses, or when neither of them is present, or when only one. When both the objects are present to the senses along with the relation, we call this perception rather than reasoning ”

“ There is nothing in any objects to perswade us, that they are either always remote or always contiguous; and when from experience and observation we discover, that their relation in this particular is invariable, we always conclude there is some secret cause, which separates or unites them. The same reasoning extends to identity. We readily suppose an object may continue individually the same, tho' several times absent from and present to the senses ”