Thanks to Dave Lull for passing along a link to an excellent essay by Thomas Keymer in The Times Literary Supplement on Johnson's Rasselas. Keymer examines Johnson's view of happiness and its elusive, dangerous qualities:
"In personal terms no less than philosophical outlook, happiness was far from Johnson’s reach when Rasselas was composed. Ten years earlier, in `The Vanity of Human Wishes', he had produced a monumental yet also heartfelt statement about the inevitable defeat of worldly ambition. Life in the poem is a condition of relentless struggle, in which mankind `Hides from himself his state, and shuns to know, / That life protracted is protracted woe'. This resonant couplet, with its equation between living and suffering, set the tone of Johnson’s writing for a decade. Closer in time to Rasselas, he famously declared (in his pulverizing review of Soame Jenyns’s Free Enquiry into the Nature and Origin of Evil, a fatuous Panglossian treatise on the benevolence of Providence) that `the only end of writing is to enable the readers better to enjoy life, or better to endure it'. Here was a formula that would re-emerge in Rasselas, in even more grimly antithetical style, with the poet Imlac’s account of life as `every where a state in which much is to be endured, and little to be enjoyed'."