In Difference and Repitition by Deleuze, he comes up with 3 syntheses of time. The first being habitus, which is the conditioning of actual experience through pre-existing material patterns for the Subject to interact with. The second is the Bergsonist coincidence of the past in the present (pure memory), and the presentation of the virtual/actual distinction over the possible/real distinction. The third is the Kantian synthesis, in which the issue with the first two syntheses is that under them the only thing which repeats in future time is the Same, or the Eternal Return as commonly interpreted from Nietzsche.
However, this is when Deleuze proposes that the third synthesis in order to break from this eternal cycle of the Same is with difference, and he gives an interpretation of Nietzsche in which what survives the Eternal Return is difference in itself, thereby giving structure for future time for the Subject.
All of this I understand, but I do not quite know how this is justified. If this third synthesis was introduced in the same place as the first or second I'm sure that his conception of time would not require the Eternal Return. In addition, he implies in his writing that some sort of conflict is made within the subject from the first two syntheses, which does not seem apparent to me.
I am asking if any of y'all know if there is any sort of real justification or necessity for the third synthesis to be the third postulated in that series of syntheses, or how the assumption of the Eternal Return is necessary, as this is not obvious or intuitive for me and seems to just come from Deleuze's desire to quote Nietzsche and Kant.