This indicates a heart free of prejudices and therefore open to truth. On the other hand, each of the two trigrams has a firm line in the middle; this indicates the force of inner truth in the influences they represent.
Wilhelm’s commentary on hexagram 61 (Chung Fu) establishes inner truth as a structural principle — a heart free of prejudice combined with firm central force — that generates conditions for mutual confidence and effective influence.
, The I Ching or Book of Changes, 1950thesis