One who can do you a deal of good or a deal of harm.

One who would quarrel about goats' wool. [A most captious person.]

Opportunity has hair in front, behind she is bald; if you seize her by the forelock, you may hold her, but, if suffered to escape, not Jupiter himself can catch her again.

Opportunity makes a thief.

Oppose not a hungry man.

Opposites attract.

Oppression causeth rebellion.

Our fears always outnumber our dangers.

Our hearts run riot in prosperity.

Our outward actions reveal our hidden intentions.

Our own house surpasses every other.

Our pillow should be our counsellor. [Sleep upon an idea.]

Out of nothing nothing comes.

Outward appearances assuming the form of virtues.

Over no home can the sign be hung: There is no trouble here.

Overdoing is doing nothing to the purpose.

Pain mingles with pleasure.

Pain of mind is worse than pain of body.

Pain past is pleasure.

Patience overtaxed turns to rage.

Peace gains a value from discord.

Perhaps you will soon find another, and a fairer, lover.

Plague seize the hindmost!

Pleasure and pain succeed each other.

Pleasure is the bait of evil.