Oops. Too late.
I looked into the definition of addiction. You can find 20 different sources with 20 different definitions. I ran into the following quite a bit -- the only problem is that they're looking at addiction from the "prescribed opiate for pain" side, very similar to Rush's situation. I'm not sure of the applicability to say, a recreational drug user, although it would appear to cover it.
The American Academy of Pain Medicine, the American Pain Society, and the American Society of Addiction Medicine recognize the following definitions and recommend their use:
I. Addiction Addiction is a primary, chronic, neurobiologic disease, with genetic, psychosocial, and environmental factors influencing its development and manifestations. It is characterized by behaviors that include one or more of the following: impaired control over drug use,compulsive use, continued use despite harm, and craving.
II. Physical Dependence Physical dependence is a state of adaptation that is manifested by a drug class specific withdrawal syndrome that can be produced by abrupt cessation, rapid dose reduction, decreasing blood level of the drug, and/or administration of an antagonist.
III. Tolerance Tolerance is a state of adaptation in which exposure to a drug induces changes that result in a diminution of one or more of the drug’s effects over time.
What is important to note is that they're not tying physical dependence or tolerance to addiction. Addiction may or may not include physical dependence or tolerance.