The answer is that there is a consistent inverse relationship between the lights and the vessels.34Within the system of Kabbala, the levels or layers of worlds descend from the more intangible, spiritual worlds to this tangible, physical world. This means that each vessel is initially very small because it is most spiritual at that stage. The vessel grows and develops the lower it descends, until it reaches the level of Malkhut, where the vessel has achieved its final form.
The opposite is true with regard to light. Since the levels devolve from the most spiritual to the physical, the “lowest” level of light (it’s “lower edge,” or nefesh) is revealed in the constructed world first, entering through the highest vessel, Keter. When the light progresses to greater revelation, triggered by the presence of vessels with greater opacity, which draw the light to them, the light of nefesh, the lowest level of light, descends to the next, lower vessel.
In this manner, the supernal light is increasingly revealed, while the preceding, higher level receives the next higher level of the light. This dynamic expresses a fundamental principle: The more the supernal light descends into the lower world and is revealed within it, the greater the drawing of divine light into the vessels of the higher worlds. It is the nature of the vessels that the higher vessels develop first in the partzuf.
Keter develops first, followed by the vessel of Ḥokhma and so on, until the vessel of Malkhut, which develops last. This is why we list the vessels in the order of Keter, Ḥokhma, Bina, Tiferet, and Malkhut, from above to below, as that is the order of their growth. The lights are the reverse. In the case of the lights, the lower lights enter the partzuf first, because initially the nefesh enters, which is the light of Malkhut, and then the ruaḥ, which is the light of Ze’er Anpin, or Tiferet, and so on until the light of yeḥida enters last.
Consequently, we list the lights in the order of nefesh, ruaḥ, neshama, ḥaya, and yeḥida, from below to above, as that is the order of their entrance, from lowest to uppermost.