Sentences and truth

A sentence says something about the board. In any world it is either true or false.

TCube(a)

Cube(a) says a is a cube. It is, so the sentence is true.

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How it works

The simplest sentences join a predicate to names. Cube(a) says the piece named a is a cube. LeftOf(a, b) compares two pieces: a sits in a column to the left of b.

A sentence has no truth value on its own. You check it against a world, the board in front of you. Move a piece and the same sentence can flip from true to false.

Worth memorizing

A sentence is true or false in a world, never both.
Change the world and the answer can change. The sentence stays the same.
A name points at exactly one piece.
a, b and c each label one piece on the board.
Predicates start with a capital letter.
Cube, Small, LeftOf and Adjoins are predicates. a and b are names.

Practice

0 of 4 right

Question 1

Small(a)

Question 2

Large(a)

Question 3

FrontOf(b, a)

Question 4

SameRow(a, b)

Next: Not, and, or¬ flips a sentence. ∧ needs both sides. ∨ needs at least one.