From 'The Commentary on the Decision says' to 'great penetration and steadfastness.' The Sub-commentary states: 'Difficulty at the Beginning: firmness and yielding first interact and difficulty arises'—this sentence explains the name of Tun.
Because the two qi of firmness and yielding are just beginning to interact, not yet having communicated their feelings, and their dispositions are not yet attuned, 'difficulty arises.'
Once firmness and yielding have already interacted, all things achieve smooth harmony, and it is no longer difficult. It is only at the moment of first interaction that difficulty exists; hence it says 'firmness and yielding first interact and difficulty arises.'
'Moving within peril, great penetration and steadfastness' explains the four virtues. Kan is peril, and Zhen is movement; Zhen is below Kan, which is moving within peril.
Initially moving within peril, difficulty moves unceasingly; about to emerge from peril, it attains 'great penetration and steadfastness.'
Great penetration is supreme penetration; that it does not mention 'advantage' is because advantage belongs to steadfastness, so it simply says 'great penetration and steadfastness.' 'The movement of thunder and rain brings fullness.'
The Sub-commentary states: Master Zhou says: 'This sentence reiterates and explains penetration.' But Tun holds two meanings: one is difficulty, and one is fullness.
Above, it explained the difficulty of Tun by the initial interaction of firmness and yielding; here, it explains fullness through the two images of thunder and rain.
It says that when the two qi of thunder and rain first interact and move to nourish the myriad things, they attain fullness, which is the meaning of penetration.
It reiterates 'penetration' because in an age of difficulty, penetration would seem inappropriate, and fearing that the meaning of penetration might be hard to understand, it specifically clarifies it. From here downward describes the natural images of Tun.
As for the commentary 'only with the movement of thunder and rain is fullness attained,' the Sub-commentary states: Master Zhou and Master Chu say: 'This explains penetration; when the myriad things are full, there is smooth penetration.'
'All brought about by the initial interaction of firmness and yielding' means that the movement of thunder and rain is also the initial interaction of yin and yang.
The fullness of the myriad things is likewise brought about by yin and yang; hence it says 'all brought about by the initial interaction of firmness and yielding.' If one focuses on difficulty, Kan is peril, as stated above: 'moving within peril.'
If one focuses on smooth penetration, Kan is rain and Zhen is movement, as stated here: 'the movement of thunder and rain.' Images are drawn according to the intended meaning, and their senses are manifold. From 'the workings of Heaven in chaos and dimness' to 'not at peace.'
The Sub-commentary states: This explains 'advantageous to establish feudatories.'
'Chaos' refers to initial foundation, and 'dimness' refers to dark obscurity; it means that when Heaven creates the myriad things at the beginning of their rough foundation, it is like being in a time of dark obscurity.
At such a time of chaos and dimness, the ruler should model himself on this hexagram of Difficulty at the Beginning, establishing feudatories to care for the creatures of all quarters, and must not rest comfortably in his affairs.
These two sentences explain the meaning of Tun through human affairs.
As for the commentary 'the body of Difficulty at the Beginning is not at peace,' the Sub-commentary states: because this difficulty and distress leaves the body restless, it is 'advantageous to establish feudatories.'
'The creation of things begins in dark obscurity': 'the creation of things' is the workings of Heaven in chaos and dimness.
'Chaos' conveys the meaning of initial rough beginning; 'begins in dark obscurity' means that when things are first created, their forms are not yet visible and their substances are not yet manifest, so they reside in dark obscurity.