No one is claiming that. Otherwise we'd have 97 million heroin users, wouldn't we?
The question is, is it more likely that a pot user would try heroin vs. a person who eats carrots trying heroin (as cited earlier)? Do you need a study to tell you what you common sense tells you?
Or are you going to sit there like a two-year-old in a highchair, kicking and screaming, demanding absolute, incontrovertible proof of that connection before you will accept it?
When will you accept that the same connection exists with people who use alcohol?
And I am not, as an adult, demanding such proof either. We, all of us, realize that such proof does not exist in this fallible world.
But I do demand some unbiased, tested results, which may or may not be sufficient proof. Yes, I need a study to prove to me what "common sense" seems to indicate. There are just too many things that "common sense" says is "right", and that are incontrovertibly wrong.
For instance, the world is not flat. The Sun does not orbit the Earth. A cannonball, even though heavier, does not fall faster than a wooden ball.
That is what the Scientific Revolution was all about ... being willing to take "common sense", received wisdom, assumptions, and put them to the test. It wasn't about putting one's fingers in one's ears and saying, "La la la, I can't hear you because I don't like what you're telling me, it goes against my common sense."
Exactly. Or... another thought. When you hang out with low-lifes who smoke pot, snort coke, etc., you are much more likely to engage in high-risk behaviors and have bad stuff happen to you. My dad always said you sink to the lowest common denominator; his advice was to soar with eagles. I did and am a better person for it.