Who is the main character in Russian Thinkers by Isaiah Berlin?

Berlin highlights many important characters in his book, Russian Thinkers. These men include novelists such as Leo Tolstoy, Feodor Dostoevsky and Ivan Turgenev, to critics and aesthetes such as Vissarion Belinsky, to agitators such as Mikhail Bakunin and populist revolutionaries such as Nikolay Chernyshevsky.