This article deals with the development and criticism of the ontological proof of God’s existence, the so-called argumentum Anselmi. Its brief description demonstrates its heterogeneity, which came to be object of criticism in the subsequet theological tradition. The most influential was the criticism put forward by Albertus Magnus and Thpmas Aquinas, who considered argumentum Anselmi as a proof of the not-being-proved existence of God. Fr. Suarez is the sole exception in the row of scholastic interpreters; he identified the viability of this argument in the internal experience. In the period of neoscholasticism (1820‒1870), the Catholic thinkers shared the opinion about the vulnerability of argumentum Anselmi, and explicitly or implicitly accepted the criticism of this proof offered by Kant. Formulations of argumentum Anselmi served the aim of translating the philosophical language of Modern Time into the language of scholasticism. However, during the modernist crisis (1900‒1910s), the necessity of a new address to argumentum Anselmi emerged. Ed. LeRoy’s disproof of the possibility to prove God’s being generated criticism from the Neo-Thomist R. Garrigou-Lagrange, who, arguing in favour of the viability of rational theology, attempted to exonerate argumentum Anselmi. Refuting the conventionalist and pragmatic understanding of truth, he employs the resources of neo-scholastic epistemology and provides grounds for the possibility to think about the reality of the supreme being. Thus, the content of argumentum Anselmi, on the one hand, gave impetus to developing various approaches to the proof of God’s existence, and, on the other hand, served as a link between the New European and post-mediaeval scholastic traditions.