From the consideration of the importance that the thomist doctrine had in the development of the philosophical thought of Edith Stein The treatment that St. Thomas Aquinas makes of the knowledge that the soul has of itself seems to us intimately related to the theme: the ipseidad in Edith Stein. Our hypothesis is that although they differ in their treatment and in the expression of the elements in play, their main theses are, in our opinion, fundamentally coincidental. From the analysis of certain texts of the Angelic Doctor, mainly from his works De veritate and the Summa Theologica, we will try to highlight his fundamental elements, the distinctions that he uses to finally make a certain parallel with some of Edith's texts. Stein. And so, let's see that the notions of intelligence and its operations are central, self-consciousness, presence, act and power, existential or direct knowledge of the soul as existing versus habitual or indirect knowledge of the essence of the soul, degrees of depth in the experience