How did St. Thomas Aquinas explain the relationship between the human soul and body?

St. Thomas Aquinas explained the relationship between the human soul and body by utilizing the Aristotelian concept of hylomorphism, which posits that all natural bodies consist of two intrinsic principles: matter and form.1

For Aquinas, the body is the matter and the soul is the "substantial form" of the human being. As the form, the soul is the principle that makes a human being what they are, providing the essential nature of the individual. Unlike other forms that are entirely dependent on matter, Aquinas maintained that the human soul is a unique, subsistent form. This means that while it is substantially united with the body to constitute human nature, it is capable of existing independently of matter.2345

Consequently, Aquinas argued that the soul is indestructible and survives the death of the body. By framing the soul as the form of the body, he established an intrinsic homogeneity between the spiritual and the material, situating humanity at the juncture of the corporeal and spiritual universes. This synthesis allowed him to uphold the immortality of the soul while affirming the importance of the individual and the physical body.6524