Pin (chess) Pin (chess) In chess, a pin is a situation brought on by an attacking piece in which a defending piece cannot move without exposing a more valuable defending piece on its other side to capture by the attacking piece. Moving the attacking piece to bring on the pin is called pinning; the defending piece so restricted is described as pinned. Only pieces that can move an indefinite number of squares in a horizontal, vertical, or diagonal line (i.e. bishops, rooks, and queens) can pin. Kings, knights, and pawns cannot pin. Any piece can be pinned except the king, since the
When a white horse is not a horse ambiguity of whether "is" means: In other words, the expression "a white horse is not a horse" is ambiguous between "a white horse is not identical with a horse" (true, because "white horse" is more specific than "horse"), and "a white horse is not a member of the set of horses" (obviously false). The Advocate in the dialogue is asserting that "a white horse is not [identical with] a horse," while the Objector is interpreting the Advocate's statement as "a white horse is not [a member of the group of] horses." An illustration of the alternative uses of "fei" may