In this paper we present an unexplored aspect of the work and work of Ivan Merz, Croatian blessed and protector of youth, from the beginning of the 20th century, a Catholic intellectual, professor and social worker, on the political engagement of Catholic believers and the principles of Catholic politics. The thematization of the principles of Catholic political action and "Catholic" politics in the minds of Ivan Merz has not been addressed so far because his main work on the subject was published posthumously, only in 2014. Originally created in 1925, two years after Merc's public action and advocacy. implementation of Catholic Action through the organization of HOS, the work provides a valuable insight into Merc's knowledge of the complex and difficult topic of political engagement of Catholics and the care that it takes place in the right way. There was a response to the main controversies of the actors of Catholic Action - how to reconcile the national interest and the legitimate political struggle of Catholics, which certain deserving and prominent Catholic intellectuals wanted to tie to the proven base of the lay organization approved by the bishops, and remain faithful to the wishes and principles Catholic action was defined and promoted exclusively as a religious-educational organization, clearly separated from politics. Merz dedicated this work to "educated circles", wanting to teach them the basic principles of Catholic doctrine of political action, to bring clear guidelines based on the doctrine of the Church, to teach them how to practice and lead "Catholic" policy that will care for the interests of the homeland and its citizens. , and explain the nature of the relationship it may have to Catholic action. The contribution of the paper is a presentation of Merc's theological thought in relation to political activity, its internal coherence and topicality in the present circumstances.