A typical example is the following. Color each hexagon of the infinite honeycomb lattice black with probability p and white with probability 1 − − p , independently of each other. Let a, b, c, d be four hexagons, not necessarily distinct. Let a ↔ ↔ b and c ↔ ↔ d be the events that there is a black path from a to b, and a black path from c to d, respectively. Then the Harris inequality says that these events are positively correlated: Pr ( a ↔ ↔ b , c ↔ ↔ d ) ≥ ≥ Pr ( a ↔ ↔ b ) Pr ( c ↔ ↔ d ) . In other words, assuming the presence of one path can only increase the probability of the other.