 The soul knows or is able to know itself in two ways. The first of them is an experiential and as if tactile sensation by which the soul undoubtedly senses that it is, lives, cognizes, wills, sees, hears, moves the body, and likewise for its other acts, whose principle and subject it knows and senses itself to be. And this [happens] to such an extent that it cannot actually know or consider any object or any act without always knowing and sensing itself to be the subject (suppositum) of the act by which it knows and considers that [object or act] … The other way of knowing itself is by reasoning. In this way the soul investigates the genera and differences that it does not know in the first way. (Summa II q. 76, pp. 146–47)