There were a few motivations going all the way back to my early political and intellectual interests. Probably the most important were agonistic.

Firstly, the political right has made major gains around much of the world. It’s hard to say whether its high-water mark has been reached but in 2018 it dominated the United States, Brazil, India, Russia, and many other countries. This inspired a lot of thinking about how to coalesce in opposition to the Right.

Second, and relatedly, I spent the better part of the past decade reading a great deal about the Right and its main intellectual currents. There is a crude, visceral kind of right-wing rhetoric that just conflates anything to the left of Ronald Reagan together — think about all these books on “race Marxism” — that see woke capitalism and liberal centrism as the second coming of [Vladimir] Lenin. But all that time reading the Right did convince me that philosophers like [Friedrich] Nietzsche and [Martin] Heidegger are correct that there are deep metaphysical affinities between liberal and socialist humanism.

In Introduction to Metaphysics, Heidegger dismisses liberalism and socialism as “metaphysically the same” in their inauthentic embrace of modernity and humanism. I think there’s truth to this, except I don’t share Heidegger’s gloomy conclusions. To the extent that liberalism and socialism are committed to reason, humanism, and securing a good life for all, the affinity is to be embraced.

Finally, I’ve always felt that leftists had more sympathy for elements of liberalism than they let on. If you ask the average leftist if they believe in freedom of religion, mobility, voting rights, or expression, they’ll say yes. If anything, they’ll insist those achievements are not safe in the hands of normie liberals. So The Political Theory of Liberal Socialism is in part an effort to make explicit those shared commitments.

I think it makes more sense to see these “differences” as a continuum rather than a categorical either/or. If anything, it’s undialectical to conceptualize different social forms in these stark ways while not recognizing the links between them — something I took from your book, actually, when you mention how Marx insists any new socialist society will be “stamped” by features of the old.

Understood as a matter of accentuation and qualitative rather than categorical distinction, a core difference with social democracy is the extent to which relations of production remained largely unchanged in many countries. Workers still largely labored for capitalists in a wage labor system, even if some valuable efforts were made to induce greater unionization or introduce codetermination mechanisms. What did change was the extent to which the state intervened to regulate the economy and redistribute wealth through social programs like the National Health Service in Britain or Social Security in the United States.

By contrast, a liberal socialist regime would have to place far more emphasis on implementing left-liberal principles in the workplace. This will mean extending liberal rights there to offset the power of bosses. But it will also mean very substantially democratizing power to eliminate the domination of what Elizabeth Anderson calls “private government.” Codetermination and unionization are good starts here, but very much just a beginning. This can be accompanied by far more substantial redistributions of wealth with the aim of not just catering to people’s needs but ensuring they get fair value from their political liberties as equal citizens.

Marx’s critique to a certain extent overshoots its target. He’s obviously absolutely correct that you cannot just change the distribution of surplus wealth however you want without also fundamentally transforming relations of production. To your earlier question, this was a core problem in many social democratic states where redistribution could temporarily reach relatively generous levels. But much of that fell apart because the power of capital resurged, which contributed to the neoliberal counterattack, as David Harvey explains.

But Mill was in many ways much less indifferent to this problem than Marx was aware of, and the same is true of many other liberal socialists. Mill’s call for workplace cooperatives was intended as part of a campaign to eventually do away with capitalists and was to be accompanied by economic redistribution and education programs to help bring about political equality. And of course, Mill was more farsighted than Marx on the need to secure rights for women, even if he was less admirable on questions like British imperialism.

Finally, it’s not obvious to me that we should always take the most uncompromising Marxist’s side in their debate with left liberals like Mill. Marx himself was a radically democratic thinker, but the way some Marxists simply dismissed important liberal ideas like checks and balances on state power or individual rights against the state would of course have a dark legacy. Mill was in some ways prophetic in warning socialists about the danger of such dismissals, and contemporary socialists don’t want to fall into the same trap as some of our forebears.

I think we need to be careful here to recognize that liberalism is really a family of liberalisms, and the same is true of socialism. Whether liberalism and socialism harmonize and reinforce each other or conflict depends in part on which members of the respective families you put together.

Socialists have rightly been very critical of the atomistic egoism of what C. B. Macpherson calls classical liberal “possessive individualism” and its ethic of endless acquisition. Socialists foregrounded how it is destructive of solidarity and community. Contemporaneously we’ve seen possessive strains of liberalism carry on within the neoliberal or “Cold War” liberal traditions, which have proven as uninspired in practice as they were uninspiring in theory. The high levels of inequalities and power led many to rightly feel that governments had no interest in ordinary people and their needs, which opened the door for figures like [Donald] Trump to mobilize those resentments, even if he doubled down on many of the worst policies in office.

But there are other forms of liberalism going back to Thomas Paine which were also critical of atomistic individualism and the ethic of endless acquisition. Paine was one of the first to call for the foundation of a welfare state, and he justified it by pointing out that property was a social institution, meaning the rich owed society a debt for their riches. Black radical liberals like Charles Mills have shown how we can begin (and it will be a long process) to divest liberalism, and for that matter many strands of socialism, of their racial and racist assumptions and move in a more genuinely egalitarian direction. These forms of liberalism are very much compatible with many forms of socialism, at least those many forms of socialism that are hostile to authoritarian states and command economies.

Liberalism in many ways anteceded socialism as the great modernist doctrine committed to liberty, equality, and solidarity for all. The ideas have roots that go back deeper still, but the liberal tradition deserves praise for raising them to revolutionary potential, as any good Marxist would point out. I think today one of the core things it adds to socialism is the need to protect individual rights and impose significant limitations on state power.

Deeper than that, one can stress how liberalism contributes a much-needed sense of anti-utopianism to the socialist tradition. Some socialists assumed that with a transition to a new social form not only would the state eventually wither away as everyone’s needs were met. Many even ascribed perfectionist expectations onto socialism and communism.

As [Leon] Trotsky once put it,

the shell in which the cultural construction and self-education of Communist man will be enclosed, will develop all the vital elements of contemporary art to the highest point. Man will become immeasurably stronger, wiser and subtler; his body will become more harmonized, his movements more rhythmic, his voice more musical. The forms of life will become dynamically dramatic. The average human type will rise to the heights of an Aristotle, a Goethe, or a Marx. And above this ridge new peaks will rise.

I don’t think that’s really plausible.

Indeed, a core insight of liberalism that can marry quite easily to socialism is that human beings might ethically and cognitively improve, but they will never be perfected and many of our most sinister features will persist as long as we do. Call it the Augustinian principle. In fact, I’d follow Ben Burgis in maintaining that a core argument for socialism should be a wariness of human nature and how easily it can be corrupted when some people enjoy enormous amounts of power and wealth.

What liberals need to learn from socialists is the importance of hope and to rediscover this commitment to ethical and cognitive improvement. Samuel Moyn wrote a great book Liberalism Against Itself that was a big influence on me. He points out how many of the Cold War liberals nipped a productive dialogue between liberalism and socialism in the bud. They insisted that any attempt to improve the world was dangerous and opened the door to authoritarianism. And they were especially concerned about granting the masses too much power. Well, it turns out their anxieties were misplaced; the door to authoritarianism opens when liberals don’t offer ordinary people the hope that suffuses socialism.

On top of that, liberals can learn from socialists how dangerous economic concentrations of wealth are, since they readily turn into concentrations of power. This is a lesson Marx taught long ago, and liberals have forgotten and had to relearn generation after generation.

Theoretically, I think there are a lot of us, going back some time, who have wanted to put the two together. The term “liberal socialism” isn’t unique to me. In the book, I claim Mill was the first “mature” liberal socialist, even if he didn’t use the term, but others like [Carlo] Rosselli and [John] Rawls explicitly used it well before I got to it.

Practically the difficulties are a lot more stark. Socialists and liberals managed a workable alliance in the face of the fascist right during World War II, and we’re much the better for it. Beyond those kinds of existentially pitched circumstances, it is difficult. Many liberals would agree with Ludwig von Mises that the core commitment of liberalism is to private property, and obviously socialists can have no truck with that. My response is that if liberalism really can be boiled down to little more than a fetish for property, it isn’t an inspiring credo worth allying with.

But I don’t think that’s true of many liberals. For plenty of people who identify with the label today, liberalism is about securing something like a dignified life for everyone, regardless of their circumstances. The goal of socialists should be to hold a mirror up to liberals and say that they cannot achieve their goals unless they’re willing to extend liberal principles about equality and freedom from domination to the economy.

Liberalism and socialism are linked historically, morally, and many would say spiritually to the great struggles for emancipation that reshaped the world between the seventeenth and twentieth centuries. At their best, both are revolutionary and forward-looking doctrines that reject the Right’s claims that there are superior persons in society who are entitled to more, and insist that it is as important that a poor single mother’s life goes as well as Elon Musk’s. That we don’t live in such a society is the fault of unjust social arrangements that can be changed for the better and must be.

If liberals don’t learn from socialists and vice versa, we might not see either doctrine survive into the twenty-first century. But if they do, liberalism and socialism will deserve more than survival: they’ll deserve loyalty and even love.