How can I persuade him to stop these thoughts?

I am trying to think of, what a helpful comment in your situation woud be. I noted the way you phrased, what seems to be your key objective -"to persuade him to stop these thoughts". First of all I think it would be better to try to convince him, because this will probably longer lasting effects, than mere persuasion. Also "stopping these thoughts" seems also a difficult, if not impossible task. After all, we don't really control our thoughts as such - they come up from we don't know where, even though it is possible to train our cultivate certain though patterns and cognitive or meta-cognitive structures and ideas.

Ultimately, what you are wishing for, is your son to be safe. At the same time you are getting scared by his ideas and plans about experiments with drugs.

It should be recognized though, that it is pretty uncommon for a teenager to rationalize and legitimize the use of drugs with rational (or half-/pseudo-rational -I don't want to argue this at this point) arguments. Most teenagers who do drugs - as a quick AI enhanced research^[1] suggested they do it for the following reasons: 

• Curiosity and experimentation
• Peer pressure and social influence
• Stress, anxiety, or depression (self-medication)
• Low self-esteem or lack of coping skills
• Family problems or parental neglect
• Easy availability of drugs
• Desire for pleasure or escape
• Media and cultural glamorization
• Genetic or biological vulnerability
• Lack of supervision or meaningful activities

In my opinion you might want to consider, what is the motivation behind your son's idea to take drugs. What does he want to achieve? Obviously he is looking for something.

Partially to me it looks as if he is looking for something deeper - especially when he is saying "Why not try heroin if the purpose of life is to optimize happiness assuming heroin provides proportionally more even if for a shorter amount of time?"

So what I am suggesting is trying to understand his deeper motivations and then trying to offer alternatives and different perspectives, that can help him to make the experiences he is looking for, without unnecessary risks.

At the same time this might be an opportunity and invitation for yourself to look deeper into yourself. What is your own relationship to risky, novelty-seeking or for that matter depth and meaning-seeking transformative experiences? I am just giving some ideas based on my own experiences - I hope this can help you in your situation.

1. ^{^}

   Sources: 

   • Steinberg, L. (2010). A Dual Systems Model of Adolescent Risk-Taking. Developmental Psychobiology, 52(3).
   • Khantzian, E. J. (1997). The Self-Medication Hypothesis of Substance Use Disorders. American Journal of Psychiatry, 154(2).
   • Brown, B. B., et al. (2008). Peer Influence in Adolescence. In Handbook of Adolescent Psychology.
   • Volkow, N. D., & Koob, G. F. (2015). Brain Disease Model of Addiction: Why is it so Controversial? The Lancet Psychiatry, 2(8).
   • UNODC (2022). World Drug Report: Adolescents and Drug Use.
   • NIDA (2023). Preventing Drug Use among Children and Adolescents.
   • Primack, B. A., et al. (2017). Exposure to Substance Use in Music Videos and Adolescent Behavior. JAMA Pediatrics.