How we cite our quotes: (Part.Chapter.Paragraph), with the exception of Part V, which runs (Part#. "Short Title". Paragraph). Part V has no numbered chapters—only title headings.
Quote #10
The ability to gaze turns the hammer into a living being, but a good carpenter must bear its insolent gaze and, with a firm hand, turn it back into a thing. It would seem then that a woman undergoes a cosmic movement upward and then downward: the flight of a thing mutating into a creature and the fall of a creature mutating into a thing. (VII.8.4)
Kundera tries to explain the difference between the male and female gaze by using the hammer/carpenter analogy. While the male gaze (carpenter) turns the female into an object (hammer), it's the "unnatural" gazing back of that object (the woman/hammer) that becomes truly harmful. When an object gazes, it's trying to regain some of its humanity. Then the game is no longer fun: the man has to work harder to re-objectify the woman.
Kundera describes this object-human-object arc just at the moment when Jan is trying to understand how he bungled the encounter with the younger woman on the train.
Quote #11
He realized he was only a hairsbreadth from bursting into laughter. But he knew that if he did, they would no longer be able to make love. Laughter was there like an enormous trap waiting patiently in the room, hidden behind a thin, invisible partition. Only a few millimeters separated physical love from laughter, and he dreaded crossing over them. (VII.9.3)
Jan has a close call with the absurdity of his own life one night while undressing with his married lover. Kundera is clear that laughter is transformative, and not usually in a positive way. He tells us that laughter originates with Satan himself, and although the angels quickly took up the habit, there's no real way of telling which kind of laughter you're witnessing or participating in.
For Jan, laughter in a sexual situation has a way of "castrating" a man, taking away the gravity of the moment and turning the sex act into something ridiculous.