 The second option is relevant because later scholastic authors (such as Suárez) tended to use the rational soul as the prototype to understand natural substantial forms as well. However, the rational soul is a self-standing spiritual substance that can exist and be conceived independently from the body with which it is united. This entails that the rational soul is not the form of the body, but simply a different, independent substance that is united with the body itself. Hence (pace scholastics), the case of the human rational soul cannot be used as a model to conceptualize ‘substantial forms’ in other (non-human) natural beings (PE I: 94).