Bernard Rousset entitled one of his last articles ‘The Implications of the Spinozist Identity of Being and Power’. He showed, beginning with his major book, The Final Perspective of the Ethics and the Problem of the Coherence of Spinozism, to what extent the concept of this identity was at the very heart of Spinoza's doctrine. But he also showed, beginning with this same work, that this concept did not simply arrive immediately in its fully articulated form, but rather that Spinoza progressively shifted from the language of participation to that of power [puissance]. Subsequently, in order to pinpoint this development more precisely, Rousset devoted many articles, always pertinent and lucid in my opinion, to determining the successive stages of the drafting of the Ethics. And his last book on Spinoza addressed the role played by Spinoza's reading of the Objections and Replies to Descartes’ Meditations. In the present chapter, I will attempt to follow Spinoza's reading of Descartes along the different paths that have since been opened, by situating myself, as it were, at their intersection. I will try to suggest that Spinoza was able to explicitly formulate this identity of being and power after a period of reflection on two of his own texts, which he undertook in 1663 – the first propositions of the Ethics and then Proposition 7 of the Principles of Cartesian Philosophy – and which led him to transform a proof for the existence of God, which has since disappeared from the text, into the one that is currently found in the Scholium to Proposition 11 of Part I of the Ethics.

We know that the drafting of the first eight propositions of the Ethics contained at least five steps: Chapter II of Part I of the Short Treatise; Appendix I of the Short Treatise; the text sent to Oldenburg in 1661 and which it is possible to reconstitute from Letters II and IV; a first version of the Ethics, different than the final version, and which is known to us from Spinoza’s correspondence with De Vries (Letter VIII from De Vries and Letter IX from Spinoza) dated February 1663; and finally the Ethics as we know it today.