I saw the real world of addiction when a close friend ended up in a drug treatment program.

The counselors there had a great definition for addiction - addiction is when something (drugs, tv, sex, coffee…) has consistent harmful impact on your life or the lives of those around you.

I like this definition because it is in terms of observables that matter. People (especially undiagnosed addicts) are masters of self deception. Losing a job, beating your wife, not paying the bills are much easier for everyone to agree on than the addict’s opinion about whether or not they have a physical dependency.

I too love coffee. I drink it everyday and enjoy it. I can easily afford it. It helps me accomplish things I want to accomplish. Studies keep coming out about how coffee is good for you. So I think the impact on my health is either neutral or positive. Do I have some sort of physical dependency? Probably - so what? Would I feel sick if I stopped cold-turkey? Probably- so what? Is all this rational? I don't care. Am I an addict? By the definition above- no!

Anyway, if you consider harming yourself or others irrational, then by definition addiction is irrational.

On an aside - I have some friends who have PhD's in economics. Every time I harass them by telling them that their discipline is flawed because it is based on the presumption of rational behavior, they ask me to point out a case of irrational behavior. Every time I do, they find a hidden (usually silly) benefit that suddenly makes the sum of the benefits outweigh the sum of the costs.