Gilson on Thomas Aquina's Existentialism

Etienne Gilson is a french philosopher and historian of philosophy and a famous theorizer in the neo - thomist tradition of 20th century philosophy. He believes that Aquinas is the only thinker in the western philosophy who has accepted the principality of existence and rejected the principality of quiddity. Undoubtedly, Aquinas absolutely preferred the act of existence to the essence. However, can we accept that Aquinas really has granted the principality of existence? Do Aquinas and Mulla Sadra have the same views of the existence-quiddity conceptual distinction? Or have not, as Gilson thinks so. More importantly, if Gilson is not right in his interpretation of Aquinas assertion of the principality of existence, then we can not accept that western philosopher have considered the problem of the principality of existence and the principality of quiddity.