The paper provides analysis of the main problem of practical discourse — the issue of substantiation of moral standards — and addresses logical foundations of the so-called principle or law of D. Hume, according to which a logical transition from “is” to “should” is impossible, that is, from descriptive judgments to normative ones. The study shows that this law does not exclude all ethical theories, but only those that justify the norms of morality, deducing them from any realities of the external world: laws of nature, direction of evolution, objective course of history, etc. Hume only limits the methods of substantiating normative propositions, but does not exclude the very possibility of justifying them. The authors discuss various types and attempts to substantiate value judgments and propose to use a new concept of normative correctness. They also perform analysis of cognitive and non-cognitive concepts (I. Kant, C. Bayer, M. Singer, D. Rawls, P. Lorenzen, E. Tugendhad, Karl-Otto Apel, J. Habermas). The paper gives preference to the cognitive approach, and within its framework — the ethics of discourse developed by J. Habermas. The central point in the ethics of discourse is the principle of universalization, which is discussed in detail. The study shows that the principle of universalization and other provisions of the ethics of discourse seem to be well-founded, and the approach itself is the most promising of all other modern ethical undertakings. It also attests to the fact that the ethics of discourse is best suited to the spirit of genuine democracy. As the authors conclude, one way to persuade people to exercise free will and to apply the principle of universalization is through enlightenment, appealing to the mind, and demonstrating that a program to substantiate the ethics of discourse is the best in clarifying our everyday moral intuitions and defending democracy.