Thomas Aquinas advocates a noticeably anti-dualistic anthropological position, which forces him to explain human beings as metaphysically complex beings. This would be impossible on the physical level alone. However, the problem of the essence of material forms is still elaborated insufficiently. As to my knowledge, there are still two questions, which have not been properly answered: (a) How should the matter in the essence of particular beings be comprehended; b) how it is possible to combine the existence of an indivisible soul with its being the very basis of intellect and the form of the body. The paper unveils Aquinas’s differentiated approach to these questions in order to suggest a new interpretation of the essence of material beings. Rendered in a wider context of Thomas’s psychology, it would comply with following requirements: a) historical-philosophical coherence, by which we mean primarily a meaningful categorization of the elaborated concept into the historical-philosophical framework; b) metaphysical coherence and c) philosophical-psychological coherence.