Towards the outside, at any rate, the ego seems to maintain clear and sharp lines of demarcation. There is only one state — admittedly an unusual state, but not one that can be stigmatized as pathological — in which it does not do this. At the height of being in love the boundary between ego and object threatens to melt away. Against all the evidence of his senses, a man who is in love declares that "I" and "you" are one, and is prepared to behave as if it were a fact.

Ch. 1, as translated by Joan Riviere (1961) - Civilization and Its Discontents (1929)