AbstractIn Ennead II 9  17 9-10 [Henry-Schwyzer] Plotinus says that, ‘there (in the intelligible world) magnitude manifests itself as (pure) power, while it appears as mass in the sensible world’ (τὸ γὰρ ἐκεῖ μέγα ἐν δυνάμει ἐνταῦθα ἐν ὄγκῳ). The paper will explain what this expression means and point out the importance it could have for a profounder understanding of the fundamental tenets of Plotinus’ metaphysics. In particular, the paper will assess whether the relationship between the material and the spiritual/intelligible dimensions can be understood more precisely by making use of the concept of ‘power’ to explain the formation of the primordial matter by the ‘shaping power’ emanated from the ideas of the intelligible world. In order to reach this goal, all occurrences of the term ‘power’ (δύναμις) in the Enneads will be duly assessed and discussed; the same will be done with regard to the term ‘mass’ (ὄγκος) and ‘magnitude’ (τὸ μέγα). On the basis of the results of the research carried out, the paper will be able to judge the thesis that the interaction of the concepts of ‘power’, ‘mass’ and ‘magnitude’ can shed a better light on Plotinus’ conception of the formation of the material dimension by the intelligible one.