Cowper suffered attacks of insanity throughout his life, and sought either treatment or retirement in an asylum early in his life. There he became interested in the predestinarian theology of John Calvin, and became devoted to evangelical Christianity. In 1767 he moved to Olney, where he wrote The Olney Hymns with the evangelical preacher John Newton. The project was interrupted by another attack of insanity, during which he was convinced of his irrevocable damnation -- a sense he describes in his last important poem, "The Cast-Away."
In 1785 he published his most famous work, The Task, a long poem in six books. Wollstonecraft quotes from The Task in A Vindication, 5.50:
A patriot's blood, Well spent in such a strife, may earn indeed, And for a time ensure, to his lov'd land, The sweets of liberty and equal laws; But martyrs struggle for a brighter prize, And win it with more pain. Their blood is shed In confirmation of the noblest claim-- To walk with God, to be divinely free, To soar, and to anticipate the skies! Yet few remember them. They liv'd unknown Till persecution dragg'd them into fame, And chas'd them up to heav'n. Their ashes flew -- No marble tells us whither. With their names No bard embalms and sanctifies his song: And history, so warm on meaner themes, Is cold on this. She execrates indeed The tyranny that doom'd them to the fire, But gives the glorious suff'rers little praise. He is the freeman whom the truth makes free, And all are slaves beside.-- The Task, "Winter Morning Walk," 714-33.