"The candle of God is the soul of man" (Proverbs 20:27). Chapter nineteen of the Tanya takes this verse and builds from it one of its most luminous teachings: the soul is a flame that constantly seeks to extinguish itself.
Watch a candle flame. It flickers upward, straining away from the wick, reaching toward nothing visible. The flame's nature is to rise, to separate from the wick that gives it form, to merge with the "universal element of fire" in the atmosphere above. If the flame succeeded, it would cease to exist—no more light, no more warmth, nothing. But that is what it wants. It yearns for self-annihilation in its source.
The neshamah (נשמה) is the same, says Rabbi Schneur Zalman. The soul does not want to be in a body. It wants to dissolve back into God, its source—even though doing so would mean losing its individual existence entirely. This yearning is not a conscious decision. It is the soul's nature, deeper than reason, beyond the reach of intellect. The Tanya says this drive comes from the faculty of chochmah (חכמה) within the soul, which is where the light of the Ein Sof (אין סוף) is clothed.
This concept—that holiness is defined by self-nullification—is the Tanya's master principle. Everything holy has this quality: it nullifies its own existence before God. The angels nullify themselves. The sefirot (the divine emanations) nullify themselves. The Hebrew word for holiness, kodesh (קדש), is related to the Aramaic koach mah (כח מה)—literally, "the power of what?"—meaning the power of nothingness, of total humility before the Infinite.
The sitra achara—the "other side"—is the exact opposite. It insists on its own independent existence. It says: "I am, and there is nothing besides me." The Tanya identifies this as the root of all evil: the claim of self-sufficiency, the refusal to acknowledge that everything comes from God and belongs to God. Holiness dissolves the self. Impurity inflates it.
This is why the soul feels restless in the body. It is a flame on a wick, endlessly reaching upward toward a home it remembers but cannot reach.