Lucian Freud (1922-2011) was interested in the telling of truths. Always operating outside the main currents of 20th-century art, the esteemed portrait painter observed his subjects with the regimen and precision of a laboratory scientist. He recorded not only the blotches, bruises, and swellings of the living body, but also, beneath the flaws and folds of flesh, the microscopic details of what lies within: the sensation,...