Marsilius of Inghen is most well known for his work in nominalism. Though no one called themselves nominalists in the 14th century, he is considered one of the movement's "forefathers." In his nominalist philosophy he accepted the basic nominalist foundation, namely that universals are only existent within the mind, and outside the mind there are only individuals. He advocated that human knowledge can be derived from a foundation of sensory knowledge. However, to Marsilius, metaphysical knowledge was the greatest obtainable form of knowledge. This is due to its ability to grasp the most highly universal propositions.