• Everyone you know that has watched a commercial for Bob’s NewWidget purchases Bob’s NewWidget and thinks that it is the greatest invention.
  • You are given the opportunity to watch the commercial.  Do you take it?
• Everyone you know that has taken a certain drug BNW purchases Bob’s NewWidget and thinks that it is the greatest invention.
  • You are given the opportunity to take the drug.  Do you take it?

Now we’ll change things slightly:

• Everyone you know who has read a certain book comes to believe that free market capitalism is the only viable economic system for the future of humanity.
  • Do you read the book?
• Everyone you know who has taken a certain drug FMC comes to believe that free market capitalism is the only viable economic system for humanity.
  • Do you take the drug?

and, finally…

• Everyone you know who has read a certain book comes to believe that God exists and has a personal relationship with them.
  • Do you read the book?
• Everyone who has taken drug BPG comes to believe that God exists and has a personal relationship with them.
  • Do you take the drug?

In all these cases, of course, we assume that there are no other side-effects of the drug/book/commercial.  Tease out what matters between these different scenarios, if anything in fact, distinguishes them.