Such an inference would amount to knowledge, and would imply the absolute contradiction and impossibility of conceiving any thing different.

But as all distinct ideas are separable, it is evident there can be no impossibility of that kind.

When we pass from a present impression to the idea of any object, we might possibly have separated the idea from the impression, and have substituted any other idea in its room.
It is therefore by EXPERIENCE only, that we can infer the existence of one object from that of another.

The nature of experience is this.

We remember to have had frequent instances of the existence of one species of objects; and also remember, that the individuals of another species of objects have always attended them, and have existed in a regular order of contiguity and succession with regard to them.