I'm slowly rereading Richard Holmes's biography of Shelley and have reached the hard-to-face point at which Shelley leaves his wife Harriet for 16-year-old Mary Godwin. This is such an ugly episode, and his self-justifications are impossible to stomach. The following is from a letter he wrote to Harriet after he had deserted her, saddled her with a stack of unpayable bills, and then tried not only to borrow money from her but also to convince her to join his new household as "a sister."

I was an idiot to expect greatness or generosity from you, that when an occasion of the sublimest virtue occurred, you would fail to play a part of mean and despicable selfishness. The pure & liberal principles of which you used to boast that you were a disciple, served only for display. In your heart it seems you were always enslaved to the vilest superstitions, or ready to accept their support for your own narrow & worldly views. You are plainly lost to me forever. I foresee no probability of change.

Harriet's side of the correspondence has been lost. A few months later she drowned herself.

It is a truism that great artists are not necessarily great human beings, and art doesn't excuse or erase cruelty or indifference. Nonetheless, the art does exist and is glorious; and like nature's (or God's) beauty, cruelty, and indifference, it is simple/complicated/impossible to explain.

But poor Harriet.