Leo Strauss was famous for his reading of Western culture, history, and politics as a division between Athens and Jerusalem. Borrowing from the Christian philosopher and theologian Tertullian, who famously bemused “What has Athens got to do with Jerusalem?”, Strauss recontextualized the question and thesis of Tertullian as one of oppositional antagonism which, nevertheless, is the root and vine of Western dynamism and greatness. Athens is archetypal for reason: the material world; Jerusalem is archetypal for revelation: the supra-rational world.
It is important not to misconstrue Strauss as arguing that the peoples who fall into the Jerusalem camp are “irrational.” Rather, they are anti-rational in the anti-materialist sense inaugurated by the pre-Socratics and, more firmly entrenched into a permanent block of Western thinking, with the late Renaissance and Enlightenment with figures like Machiavelli, Hobbes, Locke, Smith, and Ricardo. Athens emphasizes cut-throat realism, individualism, and materialism. Jerusalem emphasizes community, compassion, and a suspicion to, or outright rejection of, materialist doctrines.
The matter of leftwing politics is peculiar and befitting an ironic Straussian reading. While the political left is generally considered irreligious, secular, and generally scornful of religion and the religiously devout, it has a strong Jerusalemite integrity to it. The issue of leftwing politics, especially in its utopian form, as a bastardized and materialized (or “rationalized” or Athenianized) iteration of soteriological eschatology is already well documented in scholarship. Fyodor Dostoevsky perhaps best captured this weird interplay of Athens and Jerusalem in leftwing political thought in the pages of Brothers Karamazov, “If by chance [Alyosha] had become convinced that God and immorality did not exist, he would immediately have joined the ranks of atheists and socialists (for socialism is not just a question of labor organization; it is above all an atheistic phenomenon the modern manifestation of atheism, one more tower of Babel built without God.”
Dostoevky is insightful here in seeing this atheistic, yet moralistic, phenomenon. True rationalism, in the Athenian sense, is Thrasymachian, Machiavellian, and Hobbesian-Lockean. There is no moral order or moral nature. What is “good” is to do what is in the interest of the powerful or yourself, to best attain material comfort and advantage against others. This is rationalism in its purest form and the derivative end of the outlook of Athens which Athens itself embarked upon during the Peloponnesian War which is visibly clear when reading Thucydides. Moralism, compassion, and kindness, etc., is anti-rational; it is historically connected to God, religion, spirituality—i.e. Jerusalem. Note what Dostoevsky does not say. He doesn’t say if Alyosha was convinced that if morality did not exist that he would have become a socialist. He states that socialism is the phenomenon when one is convinced there is no God but remains convinced that morality still exists precisely because immorality is seen throughout the world. If immorality did not exist, if everyone was moral, then there would be no impetus for socialism. Because immorality does exist, which entails that there is a moral order being affronted by immoral action, socialism has the engines of momentum and fanatical fervor.
But where is this law of morality? Where did it come from? Why is the morality of egalitarianism true and the law of survival of the fittest not true? Strauss’ point, here, is that the paragons of “reason” on the moral questions exude the Jerusalemite inheritance of Western intellectual culture. Dostoevsky’s statement shows this Straussian dynamic: Leftwing politics is, ironically, and amusingly, a weird synthesis of Athens and Jerusalem.
The underlying disposition of the leftwing socialist mindset is that life is about power and material wealth and comfort (the worldview of Athens). But it is also about compassion, brotherly love—however distorted—and morality (the worldview of Jerusalem). What reason should I, or any wealthy community, be compelled to give to those less fortunate or well-off than I, or us? There is no rational justification for compassion. The justification for compassion is not the worldview of Athens but the worldview of Jerusalem; it is the “secularization” or temporalization of the Jewish-Christian ethical mindset trying to counteract the materialistic and competitive liberal mindset of the Enlightenment—typified by materialism, capitalism, and industrialization, etc.
To be truly rational is to be a cut-throat individualist libertarian or a national realist (pending on your axiomatic anthropology of a-social or social human nature). To be truly anti-rational, fully given to revelation, one would give up everything he possessed and follow Christ. The political left, then, in this Straussian reading, is neither rational nor anti-rational. It is a weird mix of the two. Which is what makes it even more problematic and self-contradictory. The left wields the language of Athens—of reason—to justify the language of Jerusalem, of revelatory and moralistic conviction, which conflates and denigrates both. The mere fact of the existence of leftwing movements in the West, as they have come to be and what they promote, is evidence of the Athens-Jerusalem dichotomy. Namely, it tries to rationalize the revelatory; it tries to moralize the material without the Author of Morality. And this is why, according to Strauss, leftwing politics which begins with the language of compassion becomes brutalizing and barbaric once it achieves power. Because its Athenian inheritance demands power politics once power has been seized.
 Fyodor Dostoevsky, Brothers Karamazov, Book 1, Chapter 5.