Do people tend to disagree over political issues because of conflicting values? Or do they disagree about which policies will most effectively promote shared values? In a previous article, I argued that the issues most people think are most important tend to fall into the latter category. On the issues of greatest importance to the mass public, most citizens agree about the ends that are desirable, but disagree about which policy means would best effectuate those ends. Consequently, disputes about facts—disputes (...) about the actual effects of proposed public policies—lie at the heart of the most important divisions in contemporary American public opinion. However, people do not necessarily interpret their political disagreements this way. If they fail to recognize that facts that they see as self-evident are disputed by their opponents, they may see their opponents as having different values, since there could be few other explanations for their opponents' disagreement with them. However, evidence that disagreements about facts are really driving public opinion can be found by using conditional surveys, which ask respondents if they would support a given policy if they believed that it would cause specific negative consequences. (shrink)