 As Taurellus explains, a form is nobler than other forms if it is more prone to cause changes in other forms, and form is less noble than other forms if it is more prone to receive the effect of the activities of other forms. Passive changes of forms thus are seen as a result of the contingent activity of other forms together with the internal constitution of the forms that have undergone change (PT: 298). In this sense, in Taurellus’s view the subordination relation between substantial forms reduces to relations of efficient causation between substantial forms. Consequently, Taurellus regards the activities of substantial forms as the origin of all of the forces found in the natural world: 