Suárez’s theory of knowledge, worked out in his On the Soul (1621), presents a significant philosophical addition to the famous Metaphysical Disputations (1597). Even if On the Soul was published posthumously, its basic thoughts were developed, by Suárez himself, as early as in the first half of the 1570’s. For this reason this work of pure philosophy provides the indispensable context for Suárez’s metaphysical reflections. The article presents the fundamental characteristics of Suárez’s theory of knowledge, with emphasis on knowledge of reason, and with a view to its critical relation to Thomist theory. It is above all Thomist theory which Suárez was addressing. Next to the brief presentation of the historical context of the work and a sketch of the basic anthropological tendencies connected with Suárez’s particular form of dualism with regard to the question of the soul and body, the author presents four basic characteristics of Suárez’s theory of knowledge. 1) Suárez’s theory of knowledge is characterised as a doctrine that puts emphasis on the vital nature of knowledge. The whole principle of knowledge cannot be considered without the factor of the attentive soul; passive reason, as really identical with active reason, cannot be treated as passive primary matter; the intentional species represent extramental objects only in an embryonic way; intentional connections of the knowing subject with the known thing can be understood as, at most, an accidental one. All these theses are clearly signs of non-Thomism. 2) Suárez’s theory of knowledge is characterised by direct cognitive realism. The rejection of the expressed species (species expressa) really distinct from the cognitive act and the rejection of the definition of a formal concept as that in which (id in quo) we grasp extramental things, shows that Suárez unequivocably advocates a conception of direct realism. He views Thomist theory as approaching too closely to an undesirable representationalism. 3) Suárez’s teaching is further characterised by a theory of the sympathy of cognitive potencies having their root in a common soul. It is this theory – widely accepted in Renaissance philosophy – which understands the relation between sensory and rational knowledge acausally. Suárez conceives it in contrast to the Thomist theory which works with a causal understanding of this relation. 4) In the final part of the study Suárez’s epistemological theory of the direct rational knowledge of material individuals is presented. Thomist teaching on the reflexive rational knowledge of individuals is rejected by Suárez for the same reason as Thomist theory on the real distinction between the concept and cognitive act: both offend against direct realism and thus also against the objectivity of our knowledge. The author comes to the negative conclusion that Suárez’s theory of knowledge is positively not primarily inspired by Thomist theory. The main influence – one which the author does not attempt to elaborate – seems to be the Augustinian-Franciscan tradition. At the same time attention is drawn to some of Suárez’s themes that are taken up by modern philosophy, such as occasionalism, innate ideas, predetermined harmony and the unity of apperception – these bring Suárez close to the conceptions of early modern rationalists.