P36: He who recollects a thing by which he was once pleased desires to possess it in the same circumstances as when he first was pleased by it.

Dem.: Whatever a man sees together with a thing that pleased him (by P15) will be the accidental cause of Joy. And so (by P28) he will {II/168} desire to possess it all, together with the thing that pleased him, or he will desire to possess the thing with all the same circumstances as when he first was pleased by it, q.e.d.

Cor.: Therefore, if the lover has found that one of those circumstances is lacking, he will be saddened.

Dem.: For insofar as he finds that a circumstance is lacking, he imagines something that excludes the existence of this thing. But since, from love, he desires this thing, or circumstance (by P36), then insofar as he imagines it to be lacking, he will be saddened, q.e.d.

Schol.: This Sadness, insofar as it concerns the absence of what we love, is called Longing.