In allusion to this the sages said: “[The congealment of the firmament] can be compared to a pot of milk (=the material substance, Judgment): as soon as a drop of rennet falls into it, it immediately solidifies” (Bereishit Rabbah 4:7). In terms of this metaphor, the resulting entity essentially derives from the milk – because the rennet is merely the catalyst. Similarly, the root of the material substance of the separate creations lies in the Strengths.
Judgment has its own functions in the government of the creations. However we are not now talking about the governmental functioning of Judgment but rather about what is born as the direct offspring of the lights of Judgment, which then function as they function in the governmental order. The offspring of the lights is the material substance of the separate creations. The subsequent government of these creations through Judgment is a separate matter. What we are saying is that out of Judgment come forth fire and gold etc. i.e. from the actual lights themselves, not through their functioning in the governmental order. Likewise, water or silver etc. come forth from Kindness – from the actual lights themselves. The functioning of the lights is a different matter: this is the “rennet” that activates the material, while the material itself comes from the lights themselves, and this is the “milk”.