The purpose of this article is to outline those essential distinctions of ethical socialism from a radical or left socialism, namely, not in the political plane, but in respect of development of "ethical" doctrines. Why the moral and legal aspect in philosophy of ethical socialism and as Kant's categorical imperative can enrich dialectic materialism, and also show why it is better to change social reality peacefully, instead of world revolutions, hat is so important. Proceeding from Cohen, Communism as telos (goal) of history unfolds through denying the existence of the rule of law and upholds the denial here of the possibility of revolution. Thus dialectical thinking seems to exclude the possibility of non-radical change through transformative steps of laws, and calls instead for a class polarization and structural violence, regardless of the empirical conditions where it is located. The very "unjustified" violence is contrary to moral principles and the categorical imperative. The categorical imperative, which dominates in thoughts of ethical socialists, is opposed to any unjustified violence and especially terror. This means that the revolutionary struggle of the proletariat is not legitimate because it is not consistent with some philosophical reasonable and predictable ideals, according to neo-Kantian socialists, but simply because It's only the struggle of the proletariat. In other words, the practical situation of the working class in the historical process legitimizes its existence and its struggle without any doubts. Habermas argues that Marx failed to see a person as an agent, which means the both a tool-making and "symbolizing" the animals, that is - labor and language are fundamental anthropological categories in the sense, that none of these categories cannot be reduced by one other. If you start to argue, then it means a return to the Hegelian - Marxist "error" and believe that "justice will inevitably turns to the extent that what should be", what history is - the judge and "happily appears" on the side of the proletariat. In our opinion we must first define and explain what is "proper" and truth, before class of proletariat could be justified. Critical ethics is logically prior and independent of historical development and such ethics prescribes that actually preaches "ethical socialism". The article also makes some parallels to universal prescriptivism of R. M. Soviet author Oleg Drobnicki which considers that they both tried in some sense to unify Kantian universalism, his main goal is not just changing concept of historical materialism, but to bring human dignity to agenda in Soviet ethics.