There is no friendship between a man and a woman

I forgot that is impossible to feel nothing but friendship for a woman whom one thinks pretty, whom one sees constantly, and whom one suspects of being in love. Friendship at its apogee becomes love, and, relieving itself by the same sweet mechanism which love needs to make itself happy, it rejoices to have become stronger after the fond act. A Platonist who maintains that one can be merely the friend of a pleasing young woman with whom one lives is a visionary.

Giacomo Casanova - History of my life (6, 7)