# Fundamental Theorem of Poker

The **Fundamental Theorem of Poker** was formulated by David Slansky. It encapsulates the essential nature of poker as a game of decision making under the conditions of incomplete information and volatility.

## Statement of the Theorem

The **Fundamental Theorem of Poker** is usually stated in natural language but is actually based on strong mathematical foundations (Law of Iterated Expectation).

- Every time you play a hand differently from the way you would have played it if you could see all your opponents' cards, they gain;
- and every time you play your hand the same way you would have played it if you could see all their cards, they lose.

Because poker is a Zero Sum game, the converse of the theorem immediately follows:

- Conversely, every time opponents play their hands differently from the way they would have if they could see all your cards, you gain;
- and every time they play their hands the same way they would have played if they could see all your cards, you lose.

## Examples

## Morton's Theorem

The Fundamental Theorem of Poker always applies to heads up poker, or when an otherwise poker game is reduced to a game of two people. It applies to multiway pots almost always, with a few exceptions.

These exceptions were first highlighted by Andy Morton in a newsgroup, after whom the principle was named Morton's Theorem.

It should be noted that Morton's Theorem is in direct contrast with the Fundamental Theorem of Poker.

**Cite as:**Fundamental Theorem of Poker.

*Brilliant.org*. Retrieved from https://brilliant.org/wiki/fundamental-theorem-of-poker/