Dr Marius S. Ostrowski FRHistS FRSA is a social and political theorist, historian of ideas, public policy researcher, pianist and composer, and writer. He is a Max Weber Fellow at the Robert Schuman Centre for Advanced Studies, European University Institute, Florence. Between 2013 and 2020, he was Examination Fellow in Politics at All Souls College and the Department of Politics and International Relations, University of Oxford.

His research addresses the question of how ideologies emerge and gain influence among the general public. His interests include the emergence of social democracy in the early 20th century, and the rise of movements in favour of European unification during the interwar period.

Latest publications

'Social democracy and "positive" foreign policy: The evolution of Eduard Bernstein's international thought, 1914​–1920', History of Political Thought 42(3) (2021), 520–64. 
In the early twentieth century, European Social Democracy was confronted with newly-salient problems of foreign and international policy thanks to rising tensions between the European 'great powers'. Eduard Bernstein, founder of 'revisionist' Marxism, played an increasingly central part in the ensuing debates within the socialist movement. Yet his position on questions of colonialism, anti-imperialism, militarism, pacifism and diplomacy has--like much of his later work--been hitherto inadequately explored and often misunderstood. This article re-evaluates Bernstein's foreign policy thought, and argues that the First World War provoked a profound shift in his views--expressed in texts that deserve wider recognition in the canon of socialist internationalism.

'How (Not) to Form a Progressive Alliance: Lessons from the History of Left Cooperation', Political Quarterly 92(1) (2021), 23–31.
Britain’s political parties can be divided into two blocs: a ‘progressive bloc’ of parties on the left/centre-left, and a ‘reactionary bloc’ of those on the right/centre-right. In three of the last four general elections, the progressive bloc won an appreciably larger share of the popular vote than its reactionary rival. Yet its greater internal fragmentation has been repeatedly punished under first past the post, leading to what is now over a decade of Conservative-led governments. This has prompted growing pressure to form a ‘progressive alliance’ between Labour, Liberal Democrats, Greens, and their Scottish, Welsh and Northern Irish nationalist competitors. This article sheds a historical and international light on these demands, examining the difficulties other similar efforts at progressive cooperation have faced across the world. It considers how progressive alliances have previously sought to overcome geographical, ideological, and social divides between their constituent members, and draws some salutary lessons for British progressives today.

Eduard Bernstein on Socialism Past and Present: Essays and Lectures on Ideology (Basingstoke: Palgrave Macmillan, 2020).
​A scholarly edition of six major texts and selected shorter writings by the social-democratic thinker and politician Eduard Bernstein, translated into English in full for the first time: Socialism Past and Present; The Social Doctrine of Anarchism; Social Liberalism or Collectivism?; How is Scientific Socialism Possible?; What is Socialism?; The Socialisation of Enterprises; and articles from the periodicals Neue Zeit and Sozialistische Monatshefte alongside several unpublished manuscripts. Written over the period 1893 to 1931, these works focus on socialism as an ideology, and trace debates about ethics, social science, and class struggle that preoccupied the early-20th-century socialist movement.