Here is a link to a classic by van der Linden. It reviews the history of the Marburg school that produced a Kantian approach to socialism.
Because of Hegel, Marxists became enemies of all forms of idealism, a gross self-limiting confusion. Look at physics: it studies matter, but its mathematics is idealist.
This study argues for three main theses: (1) Immanuel Kant’s ethics is a social ethics; (2) the basic premises of his social ethics point to a socialist ethics; and (3) this socialist ethics constitutes a suitable platform for criticizing and improving Karl Marx’s view of morality.Some crucial aspects of Kant’s social ethics are that we must promote the “realm of ends” as a moral society of co-legislators who assist each other in the pursuit of their individual ends, which requires in turn that we seek the realization of the republican state and peace between the nations. Thus hope for progress, as supported by the enthusiasm engendered among the spectators of the French Revolution, becomes pivotal to Kant’s ethics as well as other moral feelings such as moral indignation and solidarity with the victims of oppression.Kant views the moral society in the final instance as an “inner” unification of good wills. In a decisive elaboration of Kant, the neo-Kantian Hermann Cohen argues that all our social institutions, and notably economic enterprises, must instantiate the “realm of ends,” leading him to support cooperative socialism in Wilhelmine Germany. In his own words, Kant “is the true and real originator of German socialism” (1896).There are important evaluative similarities between Kantian socialist ethics and Marx, such as a condemnation of capitalism as a system of servitude and an understanding of the ideal society as a cooperative society, but only Marx contends that the ideal society does not set a moral task and that there is a dialectic operative in human history that inevitably leads to communist society. This dogmatic Hegelian understanding of history must be replaced by Kantian regulative understanding of progress in support of revolutionary praxis as moral praxis.We need a “Kantianization” of Marx, as Cohen and other neo-Kantian socialists also proclaimed in the three decades leading up to World War I. This study concludes with “A Historical Note on Kantian Ethical Socialism,” addressing, among others, Cohen, Karl Vorländer, Eduard Bernstein, and Kurt Eisner and the Munich Revolution of 1918. Their voices were largely silenced by the rise of fascism, and this study hopes to show that their voices still need to be heard.