If the Ethics were to end with the twentieth proposition of Part V, it would appear as the handbook for honest men desiring to attain the highest freedom and greatest happiness possible in this present life. Spinoza, however, does not close his reflections directly after the inventory of remedies for passional troubles and the means of affirming the power of the mind here and now. Having finished his examination of ‘everything which concerns this present life’, he ‘passes to those things which pertain to the Mind's duration without relation to the body’. The entire conclusion of the Ethics will thus be dedicated to demonstrating the eternity of the human mind or, more precisely, the intellect, since the imagination and memory perish with the body. We must note, however, that Spinoza does not break with his preceding analyses insofar as he had already prepared the ground for this demonstration. So, as corollary 2 of proposition 44 from Ethics II points out, knowledge of the second kind allows us to perceive things sub quadam aeternitatis specie, thereby paving the way for a grasping of the mind's eternity.

Still, this doctrine of salvation and the mind's eternity does not fail to surprise, for we know that in Metaphysical Thoughts Spinoza had reserved this property exclusively for God: ‘And I call this infinite existence Eternity, which is to be attributed to God alone, and not to any created thing, even though its duration should be without beginning or end.’ He did, by contrast, grant immortality to the human mind. Should we then consider the eternity of which he speaks in the Ethics to be only a variant of immortality, resembling a form of unlimited duration, as the wording of the scholium announcing the intention to analyse the duration of the mind without relation to the body suggests? If this is the case, then Spinoza would have strangely relaxed the function of this concept, for he would have broken his own admonition against assimilating eternity to a duration, even one without beginning or end. Or should we, on the contrary, take his reservations on this subject seriously and confer to finite modes the same eternity as substance? But to what extent can the finite share the lot of the infinite?