"God has made one thing opposite the other" (Ecclesiastes 7:14). The Tanya's sixth chapter maps the dark side of the soul's architecture.
Just as the divine soul has ten holy sefirot (the divine emanations) and three garments—thought, speech, and deed directed toward God—the animal soul derived from the kelipah (קליפה), the "husk" or "shell" of impurity, has ten corresponding "crowns of impurity" and three impure garments.
When a person thinks about, speaks about, or acts on desires that violate the Torah, Rabbi Schneur Zalman says, they are clothing themselves in impure garments. Not the dramatic evil of fairy tales. The banal evil of distraction, gossip, and self-indulgence—everything done "under the sun" that is not directed toward God is, in the Tanya's framework, sourced in the sitra achara (סטרא אחרא), literally "the other side."
But the Tanya introduces a crucial nuance. The sitra achara is not a simple binary. Between absolute holiness and absolute impurity, there is an intermediate zone called kelipat nogah (קליפת נוגה)—the "translucent shell." This is the realm of permitted pleasures: eating kosher food without spiritual intention, conducting business honestly but for purely personal gain, having a conversation that is neither sacred nor sinful. These activities are not holy, but they are not absolutely impure either.
Kelipat nogah can go either way. If a person eats a meal and uses the energy to study Torah or perform a mitzvah, the act is retroactively elevated into holiness. If not, it sinks into the domain of the shells. The entire material world sits in this ambiguous space—mostly dark, with sparks of light trapped inside, waiting to be extracted or abandoned.
This is one of the Tanya's most practical teachings. Holiness is not about rejecting the world. It is about intention. The same steak dinner can feed a mitzvah or feed the void. The object does not change. Only the direction does.