a yellow circle, indicating this line as the governing ruler of the hexagram Six in the second place means:

Straight, square, great.
Without purpose,
Yet nothing remains unfurthered.

The symbol of heaven is the circle, and that of earth is the square. Thus squareness is a primary quality of the earth. On the other hand, movement in a straight line, as well as magnitude, is a primary quality of the Creative. But all square things have their origin in a straight line and into turn form solid bodies. In mathematics, when we discriminate between lines, planes and solids, we find that rectangular planes result from straight lines, and cubic magnitudes from rectangular planes. The Receptive accommodates itself to the qualities of the Creative and makes them its own. Thus a square develops out of a straight line and a cube out of a square. This is compliance with the laws of the Creative; nothing is taken away, nothing added. Therefore the Receptive has no need of a special purpose of its own, nor of any effort' yet everything turns out as it should. Nature creates all beings without erring: this is its foursquareness. It tolerates all creatures equally: this is its greatness. Therefore it attains what is right for all without artifice or special intentions. Man achieves the height of wisdom when all that he does is as self-evident as what nature does.