Pseudoscience: How can I convince my friend that Bio Disc is a fraud?

At this point, you probably can't convince him. However, if you really are good friends, I would suggest that you have an informal,non-accusatory talk with him about your concerns that he is being defrauded. Tell him that as his friend, you don't want to see anything bad happen to him or see him get ripped off. Say this only once. If you are really friends, then he'll consider what you say and he will likely decide for himself that this product isn't doing what needs to be done. If you aren't that close, he'll simply continue doing hat he is doing regardless of what you think. Once people have convinced themselves of the "efficacy" of a product or service, they will remain convinced until they no longer believe it will work. There is nothing which you can say or do that will convince them otherwise.

With web sites like these if you Google some of the 'technical' terms you usually end up at another site selling the same items or very similar or with luck at sites telling you that the item is junk. you never get a Google hit that is a real science site. Notice that all the 'technical' terms are jumps to pages on the same or similar sites. As says your friend needs  to learn some critical thinking and have some lessons in snake oil detection. http://freethoughtkampala.wordpress.com/2011/04/05/bio-disc-finger-lift-demo-debunked/ http://en.wikipedia.org/wiki/Qnet

1: His 'reliable' source is a .com, a commercial domain name. 2: Tell him to read, and try to understand how the product could actually work without invalidating everything we know about the universe. If it sounds like made up pseudoscience, it probably is. 3: Placebo's are wonderful things, but you should not have to pay for a placebo. 4: Show him all the previous similar products (like that energy bracelet), which had a lot of people convinced, before it was repeatedly shown to be BS. 5: tell him to try to find a reputable , possibly well known scientist that they quote. Also look up the authors of the reputable site. They may not exists, or they may even be known for writing bullshit research. 6: Tell him that if he uses the product in front of anyone outside of family, they will automatically consider him a moron without further consideration.

Just don't try too hard.   My parents were sold out on this and till date use the disc to charge every drop of water they drink, passing it through the disc in a machine which runs for an hour and charges the water.   I too was speechless at first and just did not know what to tell my mom and it pained to think about the amount of money she spent on procuring all the accessories and discs. But then I realised its only money and if it does not harm her and brings her happiness, it must be worth it. I don't interfere much. She still believes food cooked with the bio disc charged water tastes fresher, the water she drinks feels lighter and tastes better and she feels like drinking more water because of the disc.   Infact, thanks to her, I too have a disc permanently placed on top my water dispenser which is supposed to be making the water better. But do I believe it makes the water better, I don't know, I think no, I don't. Do I feel like removing it and throwing it out? Certainly not! Because besides this disc on top of my water dispenser, I also have a small idol my family calls god and worships every day. I think there  is probably as much power in the water as there is god in the idol.   Infact, a few miles from my home, theres an entire building dedicated to a certain religion where people go and donate money to please a god. There is one more buildong full of shops where people sell uncomfortable pairs of shoes and weird clothes which people actually spend money on and think it makes them look good.   I've never done anything about those buildings so why should I care about a disc which makes my mother feel healthier because it enables her to drink more glasses of water everyday?   If it doesn't harm anyone, its fine. Just let people believe what they have to and you stay close to your own system of belief. Yes, if you have any information that it harms the user in any way, share it and file a case against the organisation selling it.

Even if you are able to produce a perfect argument from a rhetorical standpoint there is a good chance you won't be able to change his opinion. Do not even try to change his mind unless there is a realistic chance you will be able to do so.