H. P. Blavatsky

Mahat. Lit., “The great one”. The first principle of Universal Intelligence and Consciousness. In the Purânic philosophy the first product of root‐nature or Pradhâna (the same as Mulaprakriti); the producer of Manas the thinking principle, and of Ahankâra, egotism or the feeling of “I am I” (in the lower Manas).

Source: H. P. Blavatsky, The Theosophical Glossary, art. Mahat