Within Sousedík’s lifelong scholarly efforts, three key areas of interest can be distinguished:
Sousedík first became acquainted with the basics of scholastic thought was during his early theological studies. He further developed his knowledge only by self-study, deprived, under the communist regime, of contemporary literature and of the much needed contact with foreign scholars, to whom he had virtually no access before 1989.
However, in Prague libraries he discovered many little-known works of representants of the so-called Second scholasticism: authors who were active at European universities in sixteenth through eighteenth centuries. His research in this field led him to conclude that, as far as philosophy is concerned, the period was by no means a time of darkness (as most Czech historians held) but rather an era of vigorous intellectual life and development.
Sousedík came to be more deeply involved with contemporary Western philosophy after the Velvet Revolution of 1989. He identified analytical philosophy as closest to his scholastic interests since, like scholasticism, it insists on strict logical reasoning as one of its fundamental methods. This perceived affinity of the analytic and scholastic paradigms gave him the idea that the older scholastic tradition might be brought up to date by means of modern analytical philosophy and philosophical logic.
His efforts in this direction gained traction and gradually, a group of students gathered around him who followed upon his ideas in historical and systematic respects. In 2004, he he founded the journal Studia Neoaristotelica, which at first aimed chiefly at the Czech and Slovak milieu but later opened to like-minded foreign scholars.
Nevertheless, in doing that he became aware that his effort to bring Christian thought up to date runs up against the fact that contemporary Christian thought is largely inspired by ideas of the continental philosophical tradition. This gradually moved him to become intensively involved with the work of those continental philosophers whose ideas seemed to have exerted an infelicitous influence on contemporary Christian philosophy and theology. In this last period of his work he makes use of his erudition to defend Christian (or more precisely Catholic) orthodoxy.