Stalin claimed to have embraced Marxism at the age of fifteen, and it served as the guiding philosophy throughout his adult life; according to Kotkin, Stalin held "zealous Marxist convictions", while Montefiore suggested that Marxism held a "quasi-religious" value for Stalin. Although he never became a Georgian nationalist, during his early life elements from Georgian nationalist thought blended with Marxism in his outlook. The historian Alfred J. Rieber noted that he had been raised in "a society where rebellion was deeply rooted in folklore and popular rituals". Stalin believed in the need to adapt Marxism to changing circumstances; in 1917, he declared that "there is dogmatic Marxism and there is creative Marxism. I stand on the ground of the latter". Volkogonov believed that Stalin's Marxism was shaped by his "dogmatic turn of mind", suggesting that this had been instilled in the Soviet leader during his education in religious institutions. According to scholar Robert Service, Stalin's "few innovations in ideology were crude, dubious developments of Marxism". Some of these derived from political expediency rather than any sincere intellectual commitment; Stalin would often turn to ideology "post hoc" to justify his decisions. Stalin referred to himself as a "praktik", meaning that he was more of a practical revolutionary than a theoretician.