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This page is written by the game's inventor, Darren Izzard.

Philosopher's Chess

Designed by Darren Izzard


This game is a submission to the 40-square competition. Its playing surface comprises two sub-boards, one of 6x6 squares and another of 2x2, totalling 40 squares in all. (You can of course play this on a normal chess board if you cover up squares to leave a 6x6 section and a 2x2 section.)

The 6x6 board is called the "Field," and the 2x2 one is known as the "Philosopher's Mind" (or just the "Mind" for short). Activity on the "Mind" affects movement capabilities of certain pieces on the "Field."

In addition to the pawn, knight, rook and king, borrowed from conventional chess, there are three new pieces in this game, whose properties are described below. They are as follows:-

NameASCII SymbolGraphical Symbol
PhilosopherH hH h
Enlightened PhilosopherE eE e

Initial Board Layout

At the start of the game, the board is laid out like this:-

Graphical Diagram
Graphical board layout
ASCII Diagram
    a   b   c   d   e   f        o   d
  +---+---+---+---+---+---+    +---+---+
1 : r : h : n : k : h : r :  1 : t :   :
  +---+---+---+---+---+---+    +---+---+
2 : h : h : p : p : h : h :  2 :   :   :
  +---+---+---+---+---+---+    +---+---+
3 :   :   :   :   :   :   :      Mind
4 :   :   :   :   :   :   :
5 : H : H : P : P : H : H :
6 : R : H : N : K : H : R :


The king, knight, rook and pawn move mostly as in normal chess. However, the pawn may not move two squares on its initial move, nor is there any en passant. There is also no castling. Pawns may promote to a rook, a knight or a philosopher.

Regarding the new pieces, begin with the "thought." Only one thought piece exists during a game, and it never leaves the Mind board. It moves one square orthogonally.

The thought is neutral in colour, and may be moved by either player. Moving the thought is known as a "mind-move." A mind-move counts as a complete move in its own right, and, as with other moves, it may only be made if it will not result in your own king directly coming into check. Mind-moves are also disallowed if there are no philosophers or enlightened philosophers on the Field. A maximum of two mind-moves may be made consecutively.

Next, the "philosopher." The position of the thought on the Mind indicates the movement capabilities of all philosophers on the Field. Notice that, on the Mind, the two files are lettered "o" and "d". If the thought is in the "o" file, philosophers move orthogonally; whereas, if it is in the "d" file, philosophers move diagonally.

If the thought is in rank 1, philosophers move one square. If it is in rank 2, they move two squares (jumping the one in the middle).

Looking at the diagram above, you can see that, at the start of the game, philosophers are able to move one square orthogonally.

Philosophers capture by simply moving onto an opposing piece. If a philosopher takes another philosopher (or an enlightened philosopher), it is promoted to an enlightened philosopher.

An "enlightened philosopher" is similar to a normal philosopher, except that it may make either one or two moves in a single turn. If two moves are made, they must both apply to the same enlightened philosopher (apart from mind-moves which obviously apply to all philosophers, enlightened or not).

To make this clearer, here is a list of what a player who owns an enlightened philosopher may do in a single turn:-

1. move a piece that isn't an enlightened philosopher once, or
2. move an enlightened philosopher once, then move the same enlightened philosopher again, or
3. move an enlightened philosopher once, then make a mind-move, or
4. make a mind-move, then move an enlightened philosopher once, or
5. make two consecutive mind-moves, or
6. make one single mind-move, or
7. move an enlightened philosopher once.

If the opponent's king comes into check during a double move, the move does not have to stop - but the king may not be taken.

Enlightened philosophers do not promote any further.

Finally, one very important movement rule: if any move would cause the entire board (including both the Field and the Mind) to repeat any earlier position in the game, that move is disallowed and may not be made. This applies to all pieces at all times - even part-way through a multiple move (such as the enlightened philosopher may make), or when trying to get out of check. If this rule prevents a player from getting their king out of check, that counts as checkmate against that player and they lose. Of course, normal checkmate still works too.


In playing against the computer, I use the following notation. I am describing it here so you can read the example game I've provided.

Conventional moves are written as [start]-[destination], where [start] is the square the piece begins, and [destination] is the square to which it moves. For example, a3-b4 would mean "move the piece at a3 to b4."

Mind-moves are written as m[start]-[destination] (that is, the same format as conventional moves but prefixed with an "m"). So, mo1-d1 means "move the thought from square o1 to d1".

Pawn promotions are written as p[piece], where [piece] is r, n or h (for rook, knight or philosopher), and are written as a separate move after the pawn move which results in the promotion.

No extra notation is used for captures, check or philosopher promotions.

Take a Look at an Example Game


I developed the game by playing it against my own temporal-difference-based computer program, and tweaking the rules until it seemed solid enough.

The no-repetitions rule is borrowed from a game I designed a short while back called "In The Bin". Of course, many other games also use the same idea.

I haven't, to the best of my knowledge, used anything else from any other games in constructing this one.

Page written by Darren Izzard.
Page created 4th August 1999.