  For Telesio, the conservatio sui is the foundation from which all sensitive and cognitive functions arise. Defending an empirical approach in epistemology, Telesio tried to annul the traditional distinction between sense perception and reason, and he denied that there exists something like a purely mental sphere and a corresponding intellect which Aristotle in De anima III had called nous. Understanding is a process which requires sense perception and memory. According to Telesio, our memory is not visual. What we remember are movements which our spirit has experienced and given out when being in contact with external forces. If now the spirit undergoes a similar experience, for example the pain of getting burned, it will ascribe this perception to a similar or identical cause and call it ‘fire’ (DRN book VIII, ch. 1; vol. III, p. 160). The ability of making rational conclusions (ratiocinari) consists in comparing new expierences to old ones and in supplementing hidden or unknown aspects when refering them to former experiences. Telesio even suggests replacing the term intelligere with existimari and commemorari (DRN book VIII, ch. III; vol. III, p. 164f.). Intellectual understanding therefore does not mean to reach a realm of necessity and eternity, not even in mathematics, which according to Telesio arises from sensual experience and is a science of less dignity than the observation-based natural philosophy (DRN book VIII, ch. IV; vol. III, p. 176f.).