Pi / Holding Together [Union]

above: K'an The Abysmal, Water
below: K'un The Receptive, Earth

The first [six], divided, shows its subject seeking by his sincerity to win the attachment of his object. There will be no error. Let (the breast) be full of sincerity as an earthenware vessel is of its contents, and it will in the end bring other advantages.

Where does the 'sincerity' predicated of the subject of line 1 come from? The 'earthenware vessel' is supposed to indicate a plain, unadorned character; but there is nothing in the nature and position of the line beyond the general idea in the figure, to suggest the attribute.