There is a fourfold evolution in humanity and it unfolds successively--physically, emotionally, intellectually, and spiritually. Hence the mystic has to return to rebirth to complete his evolution despite his "union" which is consequently temporary. For riddance of the ego being the price of attainment, riddance of the emotional ego still leaves the intellectual ego untouched; that must be dealt with at its own level. Hence after emotional union has subsided he must cultivate his mental powers and regain it again as "intellectual union."
-- Notebooks Category 16: The Sensitives > Chapter 2: Phases of Mystical Development > # 241