The article presents a formalization of Thomas Aquinas proof for the indestructibility of the human soul. The author of the formalization—the first of its kind in the history of philosophy—is Father Joseph Maria Bocheński. The presentation involves no more than updating the logical symbolism used and accompanies the logical formulae with ordinary language paraphrases in order to ease the reader's understanding of the formulae. "The fundamental idea of the Thomist proof is of utmost simplicity: things which are destructible are destructible either per se or per accidens; but the human soul is destructible neither per se nor per accidens: therefore the human soul is not destructible". Bochenski's words required him to devote considerable effort for the sake of precision of the symbolic language that would be maximally adequate to Thomas' discourse. Moreover, I have thought it necessary to provide an ample commentary to the traditional and contemporary semantical presuppositions of Aquinas philosophical anthropology in light of Bocheński's interpretation thereof.