The system of unity (as explained here) is three steps:
1) division,
2) unification,
3) Oneness (where no parts exist at all, as all the parts are part of one complex purpose).
In this מאמר this idea plays itself out in four things:
1) The harvest,
2) The Sukka,
3) The Four Minim Lulav etc,
4) Torah.
MP3