This article, came out couple years ago in Critical Sociology ( 2005, Vol. 31 Issue 1/2), sheds some light on the quote.
Reading 'Opium of the People': Expression, Protest and the Dialectics of Religion. Andrew McKinnon Department of Sociology, University of Toronto
Abstract: --------- Marx's phrase 'opium of the people' is one of the most frequently quoted lines he ever wrote; perhaps because of that, it has been just as frequently misunderstood. By returning to the various meanings of opium in the mid-19th century, I revisit Marx's analysis, offering a way of reading the metaphor that is more consistent with Marx's dialectical method. The paper provides a revised analysis of Marx's "Towards a Critique of Hegel's Philosophy of Right: Introduction", as well as suggestions about how this new more open-ended reading can contribute to Marxian analyses of religious beliefs and practices in late capitalism. -------------
The author brings opium into the historical context of medicine. He elaborates:
"In Europe, at the beginning of the nineteenth century opium was largely an <i>unquestioned good</i>. Such was its importance as a medicine that in the first years of the nineteenth century, people would have understood "opium of the people" as something we could translate into twentieth century idiom as "penicillin of the people", By the end of the nineteenth century, however, its medical uses had largely been supplanted by other medicines, and medical and moral puritans effectively demonized opium. It is between these two periods that Marx penned opium as his metaphor for religion. In 1843, it is an ambiguous, multidimensional and contradictory metaphor, express both the earlier and later understanding of the fruit of the poppy".
The article was republished under a different heading in _Marx, critical theory, and religion : a critique of rational choice_ / edited by Warren S. Goldstein, which has few other interesting articles as well.
--sharif
-- Sharif Islam http://www.sharifislam.com Research Programmer University of Illinois, Urbana-Champaign Library Systems Office 217-244-4688