The second hexagram is six broken lines, the exact inverse of the first, and the relationship between the two is the structural foundation of the entire book. Every other hexagram is a mixture; these two are the poles the mixtures are made from.
Its judgement, in Wilhelm's rendering, promises success through the perseverance of a mare, counsels that one who tries to lead will go astray and one who follows will find guidance, and gives directions, the southwest furthers, the northeast means losing friends. Those compass directions are among the clearest signs of the text's origins: they are practical instructions to somebody about to make a journey, not metaphors, and they belong to the oldest divinatory stratum.
The mare is worth pausing on. It is not a passive animal. A mare is strong, and the image is of strength that carries rather than strength that initiates, which is a considerably more interesting proposition than the word "receptive" suggests in English. Translations that render the hexagram's name as Yielding, Responding, or simply Earth, all catch something Wilhelm's Receptive does not.
Like the first hexagram this one carries an extra statement, "use six", applying when all six lines change and the figure becomes its opposite. Wilhelm reads it as lasting perseverance furthering. What that instruction is actually for is not stated in the text and has been disputed since the Han period.
The convention of reading this hexagram as the complement of the first rather than as its inferior is worth defending. Nothing in the line texts ranks them, and the sequence puts them together precisely because neither functions without the other.