Boris Nikolaevich Bugaev (), better known by the pen name Andrei Bely or Biely (; – 8 January 1934), was a Russian novelist, Symbolist poet, theorist and literary critic. He was a committed anthroposophist and follower of Rudolf Steiner. His novel Petersburg (1913/1922) was regarded by Vladimir Nabokov as the third-greatest masterpiece of modernist literature. The Andrei Bely Prize (), one of the most important prizes in Russian literature, was named after him. His poems were set to music and performed by Russian singer-songwriters. Life Boris Bugaev was born in Moscow, into a prominent intellectual family. His father, Nikolai Bugaev, was a noted mathematician who is regarded as a founder of the Moscow school of mathematics. His mother, Aleksandra Dmitrievna (née Egorova), was not only highly intelligent but a famous society beauty, and the focus of considerable gossip. She was also a pianist, providing Bugaev his musical education at a young age. Young Boris grew up at the Arbat, a historical area in Moscow. He was a polymath whose interests included mathematics, biology, chemistry, music, philosophy, and literature. Bugaev attended university at the University of Moscow. He would go on to take part in both the Symbolist movement and the Russian school of neo-Kantianism. Bugaev became friendly with Alexander Blok and his wife; he fell in love with her, which caused tensions between the two poets. Buagev was invited but was unable to attend their wedding due to his father's death. Nikolai Bugaev was well known for his influential philosophical essays, in which he decried geometry and probability and trumpeted the virtues of hard analysis. Despite—or because of—his father's mathematical tastes, Boris Bugaev was fascinated by probability and particularly by entropy, a notion to which he frequently refers in works such as Kotik Letaev. As a young man, Bely was strongly influenced by his acquaintance with the family of philosopher Vladimir Solovyov, especially Vladimir's younger brother Mikhail, described in his long autobiographical poem The First Encounter (1921); the title is a reflection of Vladimir Solovyov's Three Encounters. It was Mikhail Solovyov who gave Bugaev his pseudonym Andrei Bely. In his later years Bely was influenced by Rudolf Steiner’s anthroposophy and became a personal friend of Steiner's. His ideas covering this philosophy included his attempts to connect Vladimir Solovyov's philosophical ideas with Steiner's Spiritual Science. One of his notions was the Eternal Feminine, which he equated it with the "world soul"