Stefan Swiezawski was above all a historian of philosophy, a medievalist and a philosopher interested primarily in metaphysics, but also in methodology. In his 'History of European Philosophy of the 15th century' he discussed various opposing intellectual tendencies, primarily the two dominating trends of the time: scholasticism (theocentrism) and humanism (anthropocentrism). He described the beginning of the process that would lead to the collapse of metaphysical realism. It must be emphasised, however, that he was interested not only in the currents of 15th-century thought, but also in the culture of the entire epoch in all its variety and richness. Swiezawski also tried to contribute to a better and fuller description of historiography, in particular the historiography of philosophy. He emphasised taking into account all possible historical conditions that influenced a particular author. He underlined the importance of careful analysis of texts with particular reference to the philosophical problems discussed. As a philosopher, he was interested in realistic metaphysics, which, in his opinion, was best suited to human needs for truth, the understanding of origins, completeness, ultimate ends and meaning (in an existential, rather than linguistic, sense). He criticised Thomism in its various forms, while also attempting to rehabilitate what he saw as the true thought and significance of Thomas Aquinas.