  He concludes his arguments for the existence of the intelligible world by stating that the ideal world is better known than the natural world because it is necessary, eternal and immutable. As Descartes had argued, the senses are part of the natural world and are designed to assist in preserving the union of soul and body, or to keep one alive, not for delivering knowledge. The nature and existence of the intelligible world is discovered by intellectual activity; the highest degree of intellectual activity is the clear and distinct perception.