Alice: "I cannot believe some states have made marijuana legal. If you make it legal, then you are telling teenagers that there is nothing wrong with getting high. This will create a generation of potheads who drop out of high school, get fired from their jobs, and eventually mug people to feed their addiction. Furthermore, everybody knows that weed is gateway drug. Kids who start smoking weed end up overdosing on crack and heroine. We need to keep weed illegal and keep our children safe."
Bob: "I think you need to chill out. The vast majority of people who smoke weed do not become addicted either to it or to more dangerous drugs. Also, studies show that employees who get high are more likely to get promoted than employees who do not, and there is very little correlation between marijuana use and other crimes. If weed were really as dangerous as you say, then I would agree with you about banning it, but weed is actually less harmful physically and mentally than alcohol."
Clearly, Alice and Bob disagree about whether we should make marijuana legal, but is their disagreement a moral one or a causal one?