The core philosophy of the SGI can be summed up by the concept of "human revolution." This is the idea that the self-motivated inner change of a single individual positively affects the larger web of life and results in the rejuvenation of human society. The SGI movement has its roots in the life-affirming philosophy of Nichiren, a Buddhist monk who lived in 13th-century Japan. Nichiren felt passionately that Buddhism should enable people living in the real world and facing real problems to become empowered and change their lives for the better. Nichiren Buddhism stresses the profound connection between one's own happiness and the happiness of others.