The author describes two constitutional principles – a principle of republic form of government and a principle of common good according to Basic Law of the Federal Republic of Germany (FRG) and German constitutionalists. In the general and common meaning, republican state is an opposite of a monarchy order, which also excludes any forms of autocracy and all the more totalitarianism. In fact, many German scholars underline the ancient roots of republicanism as described by Aristotle or Cicero and its material and not only formal sense. According to them – a state as res publica is a commonwealth in which all citizens have its part, every authority has an obligation to serve citizens but also every citizen is obliged to act for the common good of others. Unfortunately, the Basic Law of FRG does not contain many provisions on these issues. The republic form of the government in Germany results from article 20 par. 1, article 28 par. 1 in conjunction with article 79 par. 3 of Basic Law (eternity clause). It is very often underlined that the essence of republicanism is fundamental rights – in other words – a true republic is a system of freedom. Also other, similar terms as common welfare, common good and good of the people mentioned only in four provisions of the Basic Law – article 14 par. 2, ar- ticle 56 in conjunction with art. 64 par. 2 and article 87e par. 4 are simply not defined. Some scholars are of an opinion, that that was intentional. Common welfare is an idea, which has meta-legal, and non-state character and which is even beyond the constitution. On the other hand it just cannot be described precisely, because in every concrete case some other definition has to be elaborated by the legislators, executive and the judiciary.