The infant is the book's most frequent human image, appearing in chapters ten, twenty, twenty-eight and here, and this is the only chapter that describes one in detail rather than invoking it.
The description is deliberately physical and slightly startling. Its bones are weak and its sinews soft, and yet its grip is firm. It knows nothing of union, and yet its member stirs. It howls all day without going hoarse. Poisonous insects do not sting it, wild beasts do not seize it, birds of prey do not carry it off.
Each observation is chosen to show capacity without the usual basis for it. Grip without muscle. Sexual response without desire or knowledge. Sustained volume without strain. The chapter names the reason in the last two cases: the essence is at its height, and the harmony is at its height. Neither is an achievement and neither was worked for.
That is what makes the infant a better figure for this book than a sage would be. It is not a model of innocence to be recovered morally, and nothing here is about purity or gentleness. It is an instance of the general claim that efficacy comes from a condition rather than from effort, and the newborn is simply the clearest case available.
The claim about insects and beasts belongs with chapter fifty, where the rhinoceros finds nowhere to put its horn. In both places invulnerability is asserted, and in both it is offered as a consequence of the subject's condition rather than as protection from outside.