| Type | Inductive logic |
|---|---|
| Players | 3-8 (best with 4 or 5) |
| Skills required | Invention, induction |
| Cards | 52 |
| Deck | Anglo-American |
| Playing time | 60 minutes upwards |
| Random chance | Low |
| Related games | |
| Mao | |
Eleusis is a multi-genre card game where one player chooses a secret rule to determine which cards can be played on top of others, and the other players attempt to determine the rule using inductive logic.
The game was invented by Robert Abbott in 1956, and was first published in Martin Gardner's Scientific American column in June 1959. A revised version appeared in Gardner's July 1977 Scientific American column.
Eleusis is sometimes considered an analogy to the problems of scientific method. It can be compared with the card game Mao, which also has secret rules that can be learned inductively. The games of Penultima and Zendo also feature players attempting to discover inductively a secret rule or rules thought of by a "Master" or "Spectators" who declare plays legal or illegal on the basis of the rules.
The formalisation of Eleusis+Nobel inspired new modes of communication by exchange of logical notes.
In 2006, John Golden developed a streamlined version of the game, intended to assist elementary school teachers in explaining the scientific method to students. Abbott himself considers the variant a "great game", and refers to it as "Eleusis Express".
To play Eleusis Express, each player is dealt 12 cards, and the dealer decides on a rule on how a card can correctly be played (such as "alternate red then black cards" or "alternate cards with a closed loop (e.g. 4, 6, 8, 9, Q, A) and those without"). The object of the game is to empty the player's hand. Once a player thinks they have figured out the rule then they can declare themselves a "prophet" and make the good/bad card calls for the dealer.
An incorrect card goes below the line of cards starting a sideline. Players making an incorrect play draw another card.
If a player thinks he cannot play a legitimate card, he may declare a no play, and show his hand to everybody. If incorrect the dealer plays the correct card and gives the player another card. If the player is right the dealer replaces the player's hand with a smaller hand (with one less card) from the deck.
The round ends with a player running out of cards or a player correctly guessing the rule. At the end of the round a player scores 12 points minus the total of cards he has in his hand. The full game ends once everyone has had a chance to be dealer.