Black Mass (2007) picks up where Straw Dogs left off and makes the historical case for what Straw Dogs argued philosophically. Its thesis: the great political catastrophes of the 20th century were not aberrations from the Enlightenment project. They were expressions of it.
Gray's intellectual genealogy goes like this. Judaism introduced into Western thought the idea of a linear, meaningful history: time as a narrative moving toward a final redemption, a messianic end-state in which suffering is overcome and justice is established. Christianity took this structure and universalized it: the whole of history is the story of fall, suffering, and redemption, and this redemption is available to all humanity, not just a chosen people.
The Enlightenment did not abandon this structure. It secularized it. The messianic end-state became the ideal of reason, or freedom, or classless society, or human rights. The agents of redemption became the rational philosopher, the revolutionary vanguard, the progressive political party. The tools of redemption became science, technology, education, and political organization. But the deep structure of the narrative, history moving toward a meaningful end in which the human problem is solved, remained exactly the same.
This matters because the messianic structure of thought has a specific and consistently observed feature: it justifies present suffering in the name of future salvation. If you believe that history is moving toward a final end-state that will vindicate everything, you can justify an enormous amount of violence, coercion, and human cost as necessary for the achievement of the end. The Bolsheviks were not psychopaths (though some were). They were utopians who genuinely believed they were building the classless society that would end human exploitation. The Jacobins believed they were building the rational republic of freedom. The neo-conservatives who invaded Iraq believed they were bringing liberal democracy to the Middle East. In each case, the messianic narrative licensed violence that any honest assessment of human costs would have refused.
Gray is making a claim that is uncomfortable across the political spectrum. On the left: Marxism and socialism, in their revolutionary forms, are not just tactically failed projects. They are structurally similar to religious millenarianism, and they fail for the same reason religious millenarianism always fails: they misunderstand human nature. On the right: neo-conservatism and liberal imperialism are not realist projects of self-interest but utopian projects of global transformation, and they have produced the same combination of confident optimism and catastrophic results that characterizes all utopianism. On the liberal center: the Fukuyama thesis, that history has reached its end-point in liberal democracy and market capitalism, is another version of the messianic narrative, equally blind to its own assumptions.
A clarification that is important: Gray is not saying political action is pointless, or that all political projects are equally bad. He is saying that political projects premised on transforming human nature, on producing a permanently better kind of human being through the right institutions or the right ideology, are delusional and dangerous. Projects premised on managing human nature as it actually is, limiting the damage that human vices can do, protecting specific freedoms and specific people from specific threats: these are defensible. The difference is between politics as damage limitation and politics as salvation.