Based on this idea he explains how our current state of exile is a state of crying, a loss of the light of our eyes. Furthermore, the Tzaddik, through kiddush HaShem, can inspire us and return the light of our to us, so that we might introspect and better ourselves. In this way, the Tzaddik is even responsible for the dwelling places of the Jewish people, for it is through him that the light is returned to their eyes and their dwelling places can then be properly filled with the revealed light of their intellect. (Like the relationship of Shabbath (another name for a Tzaddik) with the Beit HaMikdash (the universal home))
This was a rare experience for me, learning a Torah while living it at the same moment. The reason is, it is only through the direct intervention of Rav Mordehai Eliyahu (may he have a complete recovery speedily in our days!) that we live in our apartment. You see, the owners didn't want to rent, but they asked Rav Eliyahu whether they should or not, and he told them to rent it out; we were the first couple to see the apartment---and to top it off, Rav Eliyahu married us a month later.
Anyways, back to the point at hand. This is a very lofty Torah of Rebbe Nachman, and bringing it down into terms that are relevant to us on a daily level is not easy. Which is why we have to be thankful that Rav Natan (Rebbe Nachman's main disciple) fleshed out his ideas in Likkutei Halachoth. (Tefillin Halachah 5 (i think)) Rav Natan explains that the parshioth in our tefillin represent the intellect, the mochin, and that is why they fill the batim, the bayit, the house of the Tefillin. The house is illuminated by the intellect.
So, while we may not be able to fully grasp the depth of Rebbe Nachman's Torah, every time we put on tefillin, we can stop and think for a moment about how the light of parchments fill and give life to the housing of the tefillin, so that all may see us crowned with the name of HaShem.
[But what about Shabbath? On Shabbath we don't wear tefillin.. But Rebbe Nachman taught us above that it is the very light of Shabbath that illuminates the Beit HaMikdash. When we walk into a Jewish home on Shabbath, the illumination is 100% palpable---Shabbath is inseparable from the Jewish home.]