QUOTE
I have taken morphine for acute pain. Any opiate that effectively relieves pain to an equal degree relieves withdrawal symptoms. The conclusion is obvious: Any opiate that relieves pain is habit forming, and the more effectively it relieves pain the more habit forming it is. The habit forming molecule, and the pain killing molecule of morphine are probably identical, and the process by which morphine relieves pain is the same process that leads to tolerance and addiction. Non habit forming morphine appears to be a latter day Philosopher's Stone. (Burroughs, p. 241).
Burroughs, William S. (1959), Naked Lunch, Castle Books. Appendix, pp. 239–255, "Letter From A Master Addict To Dangerous Drugs", letter dated 3 Aug 1956, originally published in The British Journal Of Addiction, Vol. 53, No. 2.