Complex sentence: In 1921, he returned to Moscow, where he was appointed to the chair of philosophy in Moscow University and joined the philosopher Nikolai Berdyaev, who was directing the Free Academy of Spiritual Culture.
Split into simpler sentences: In 1921, he was appointed to the chair of philosophy in Moscow University. There he joined the philosopher Nikolai Berdyaev, who was directing the Free Academy of Spiritual Culture.