Marco Rosci's biography, Leonardo (1976) notes that Leonardo "adopted an empirical approach to every thought, opinion, and action and accepted no truth unless verified or verifiable, whether related to natural phenomena, human behavior, or social activities." Rosci further noted that "he put his faith in the logical, empirical evidence of the senses and the certainty of mathematics." Also: "We know that Leonardo increasingly advocated an 'un-Christian philosophy' concerning man and nature and indulged in symbolic imagery during the first decade of the new century.
