Thus we remember, to have seen that species of object we call flame, and to have felt that species of sensation we call heat.

We likewise call to mind their constant conjunction in all past instances.

Without any farther ceremony, we call the one cause and the other effect, and infer the existence of the one from that of the other.

In all those instances, from which we learn the conjunction of particular causes and effects, both the causes and effects have been perceived by the senses, and are remembered But in all cases, wherein we reason concerning them, there is only one perceived or remembered, and the other is supplyed in conformity to our past experience.
Thus in advancing we have insensibly discovered a new relation betwixt cause and effect, when we least expected it, and were entirely employed upon another subject.

This relation is their CONSTANT CONJUNCTION.
Contiguity and succession are not sufficient to make us pronounce any two objects to be cause and effect, unless we perceive, that these two relations are preserved in several instances.