  The identification of form and substance is a feature of Aristotle’s system that Aquinas effectively exploits in this context, identifying soul, intellect and form, and treating them as a substance. (See, for example, Aquinas (1912), Part I, questions 75 and 76.) But though the form (and, hence, the intellect with which it is identical) are the substance of the human person, they are not the person itself. Aquinas says that when one addresses prayers to a saint – other than the Blessed Virgin Mary, who is believed to retain her body in heaven and is, therefore, always a complete person – one should say, not, for example, ‘Saint Peter pray for us’, but ‘soul of Saint Peter pray for us’. The soul, though an immaterial substance, is the person only when united with its body. Without the body, those aspects of its personal memory that depend on images (which are held to be corporeal) will be lost.(See Aquinas (1912), Part I, question 89.)