Critique of Hegel's Philosophy of Right.
Religion is the sigh of the oppressed creature, the heart of a heartless world, just as it is the spirit of a spiritless situation. It is the opium of the people. Karl Marx, Critique of Hegel's Philosophy of Right.There is a general lesson and a particular point to be drawn of this. The general is that the scholarly discipline requires us not to take popular understandings without turning to the source: this itself a specific case of the even more general moral that one musn't take second hand information when first hand is available.
Update: The particular lesson is that in Marxism's aggressively hostile stance toward religion we have yet another of the sadly common cases of followers corrupting the pure and simple message of the founder. Marx certainly demystified religion -- accomplishment radical enough for his purposes --but he saw its benefits: one might even say he affectionately saw its benefts. Indeed, his use of the term Opiate is itself affection -- for Marx is representing opium as the anæsthetic boon for which it was intended, not the demon bane of its perverted recreational use.
My thesis, then, of the representation of herion addiction in Trainspotting is, in part, Irvine Welsh`s fictional portraiture of a society -- modern Scotland -- where Religion is, if not absent then effectively dead and thus the Opiate of the people is....simply Opiates.