As already mentioned, he accepted that knowledge is made evident via sensory knowledge, i.e. he was an empiricist. However, he also accepted a priori truths to be an acceptable source of scientific knowledge. Also noteworthy is Marsilius’ theory behind impetus. Following in the footsteps of Buridan, Marsilius rejected the Aristotelian theory and claimed that such forces are the transfer of some property from that which did the affecting into the affected object.