Some clustering of logically unrelated beliefs could be explained cognitively—for instance, by the hypothesis that some people tend to be good, in general, at getting to the truth (perhaps because they are intelligent, knowledgeable, etc.) So suppose that it is true both that affirmative action is just and that abortion is morally permissible. These issues are logically unrelated to each other; however, if some people are in general good at getting to the truth, then those who believe one of these propositions would be more likely to believe the other.
But note that, on this hypothesis, we would not expect the existence of an opposite cluster of beliefs. That is, suppose that liberal beliefs are, in general, true, and that this explains why there are many people who generally embrace this cluster of beliefs. (Thus, affirmative action is just, abortion is permissible, welfare programs are good, capital punishment is bad, human beings are seriously damaging the environment, etc.) Why would there be a significant number of people who tend to embrace the opposite beliefs on all these issues? It is not plausible to suppose that there are some people who are in general drawn toward falsity. Even if there are people who are not very good at getting to the truth (perhaps they are stupid, ignorant, etc.), their beliefs should be, at worst, unrelated to the truth; they should not be systematically directed away from the truth. Thus, while there could be a ‘true cluster’ of political beliefs, the present consideration strongly suggests that neither the liberal nor the conservative belief-cluster is it.
Michael Huemer, ‘Why People Are Irrational about Politics’, in Jonathan Anomaly, Geoffrey Brennan, Michael Munger & Geoffrey Sayre-McCord (eds.), Philosophy, Politics, and Economics: An Anthology, Oxford, 2016, p. 458