"The best lack all conviction, while the worst are full of passionate intensity," from his poem The Second Coming, I believe.

Since I learned the poem from Joni Mitchell's rendition of it, I cannot simply think that line in my head - it is always to music, and always in her voice.

@AmyTheBruce got a link? ty

@bbyrd009 I have some trouble posting links from my tablet (surely my own fault, and not a problem with the technology). I can copy and paste, though, so here is the poem. Lines 7 and 8.

The Second Coming
Turning and turning in the widening gyre
The falcon cannot hear the falconer;
Things fall apart; the centre cannot hold;
Mere anarchy is loosed upon the world,
The blood-dimmed tide is loosed, and everywhere
The ceremony of innocence is drowned;
The best lack all conviction, while the worst
Are full of passionate intensity.

Surely some revelation is at hand;
Surely the Second Coming is at hand.
The Second Coming! Hardly are those words out
When a vast image out of Spiritus Mundi
Troubles my sight: somewhere in sands of the desert
A shape with lion body and the head of a man,
A gaze blank and pitiless as the sun,
Is moving its slow thighs, while all about it
Reel shadows of the indignant desert birds.
The darkness drops again; but now I know
That twenty centuries of stony sleep
Were vexed to nightmare by a rocking cradle,
And what rough beast, its hour come round at last,
Slouches towards Bethlehem to be born?

Yeats

@AmyTheBruce