Full Idea
The libertine is giving up something if he chooses to adopt a pious form of life. He likes sin. If God is not, the worldly life is preferable to the cloistered one.
Clarification
A 'libertine' pursues pleasure
Gist of Idea
The libertine would lose a life of enjoyable sin if he chose the cloisters
Source
comment on Blaise Pascal (Pensées [1662], 418 (233)) by Ian Hacking - The Emergence of Probability Ch.8
Book Reference
Hacking,Ian: 'The Emergence of Probability' [CUP 1975], p.68
A Reaction
This is a very good objection to Pascal, who seems to think you really have nothing at all to lose. I certainly don't intend to become a monk, because the chances of success seem incredibly remote from where I am sitting.