simple inevitability

[In Yeats’ “Adam’s Curse”] the poet remarks that writing poetry is a thankless task, for, paradoxically, the poet’s efforts are devoted to making the finished poems seem natural and effortless. Since the best poems give no evidence of the sheer hard work that has gone into their making, they win no praise from the mass of humanity, ‘bankers, schoolmasters, and clergymen’, who reserve their respect for the kind of hard work that shows.
[…]
The poem as a whole has the beautiful simplicity, the result of unobtrusive hard work, such as is mentioned within it. The colloquial vigour of the first line, for example, ensures that there is no trace of self-dramatisation here, and the language as a whole has the kind of simple inevitability that is the mark of the greatest poetry.

—Raymond Cowell, William Butler Yeats (Arco Publishing Co., 1970), p. 34-35