From the introduction by Michael Hamburger:
"Baudelaire's prose poems were written at long intervals during the last twelve or thirteen years of his life. The prose poem was a medium much suited to his habits and character. Being pre-eminently a moralist, he needed a medium that enabled him to illustrate a moral insight as briefly and vividly as possible. Being an artist and sensualist, he needed a medium that was epigrammatic or aphoristic, but allowed him scope for fantasy and for that element of suggestiveness which he considered essential to beauty. His thinking about society and politics, as about everything else, was experimental; like the thinking of most poets it drew on experience and imagination, rather than on facts and general arguments. That is another reason why the prose poem proved a medium so congenial to Baudelaire."