People subscribe to a set of beliefs because they identify themselves as members of a tribe—the left-wing or right-wing tribe. Thus they support whatever policy their team happens to support at a given moment. As Lewis puts it, “if the right-wing team is currently in favor of tax cuts and opposed to abortion, then those who identify with that team will adopt those positions as a matter of social conformity, not because both are expressions of some underlying principle.”

Issues like abortion, tax policy, immigration, criminal justice, and environmental regulation are mostly unrelated, so believing that (say) abortion is immoral, shouldn’t commit you to believe that (say) taxes are too high. Yet as Lewis points out, people’s opinions on these issues tend to travel together, as it were. Tribalism is a good explanation for why many Americans’ constellation of policy positions often are what they are: people first come to identify with a political party and only later do they come to accept all or most of its policy positions, even when the issues themselves are orthogonal to each other.

to approach the left/right split it might be best to start by wholly abstracting from political practice in order to enter the realm of political theory. In this context, political practice refers to the actions of politicians, social movements, and other political actors in the real world. Political theory, meanwhile, refers to the written or spoken articulation of political doctrines, either by writers (in their treatises) or politicians (in their speeches). Practice refers to what political actors actually do; theory refers to the normative justifications given for what ought to be done.

The main distinction between left and right is that the left advances a politics of egalitarianism, while the right opposes the left and attempts to defend some other value—tradition, for example, or individual freedom, or public order.

whatever its language, form, and following, it makes the assumption that there are unjustified inequalities which those on the right see as sacred or inviolable or natural or inevitable and that these should be reduced or abolished.

Consider some of the political ideologies we now refer to as leftist: socialism, radical feminism, and anti-racism. The three of them share a commitment to eradicating some system of power that is deemed to be unequal and hence unjust—respectively wealth, gender, and racial inequality.

leftists derive more egalitarian policy prescriptions from their view of equality than conservatives do, even if both can agree that all humans are of equal moral worth.

this analysis of the left/right split works best at the level of theory, as an ideal-type representation of both camps. The left claims to fight on behalf of equality, while the right claims to oppose the left and fight on behalf of individual freedom, or of social order, or some other value different from equality. In practice, both sides often fail to live up to their ideals; sometimes they even betray them entirely.

Across both time and space, leftists have sought to promote some strong version of equality, while rightists have sought to defeat the left and defend some other primary value.

Theories are helpful to the extent that they explain certain phenomena, and the left/right political spectrum does explain two of the main political-philosophic camps in modern history: those whose highest value is equality, and those whose highest value is both different from equality and, in their view, at odds with it.