2 Metaphors for inexorable

My own experience as child and parent convinces me that an inexorable, though mild, physical punishment is the only remedy for the obstinacy of certain fractious child natures, in the years before reason operates, and for the assurance of necessary discipline in families.

But for a man to get into a fighting attitude at the barest suggestion of sentiment; to believe in nature as something inexorable, and to aim at being as inexorable as nature: is not that almost as bad?" "Do you know any such man?

2 Metaphors for  inexorable