Abstract In the light of the analysis of Avicenna’s definition of “nature” we can discover the main principles of his physics, which are: ‘The agency of the nature’, ‘the directness of this agency’, ‘the natural object’, and ‘the essential agency of the nature’. One of the main consequences of this analysis is that the nature could be considered as the direct cause of the motion, immobility and spatial balance of the material objects. Moreover, it shows that natural objects are essentially (...) capable of possess natural properties. Accordingly, Avicenna considers that the natural properties are the same as the essential properties, which material objects have them necessarily. (shrink)