  Conviction should be accompanied by consensus, and only sense perception can claim consensus among honest investigators. Wright often acknowledged there were legitimate sources of belief besides sense perception — faith or rational introspection for instance — but none of them were adequate as sources of knowledge. Wright did not analyze sense experience into sense data, preferring to trust the holistic character of ordinary experience and most scientific observation. He introduced no theory of perception nor did he address the possible contamination of sense experience by preconceived notions. He rather placed the weight of conviction upon the employment of verification, which he allied at different times with scientific method, the philosophical doctrine of induction, and Comte's positivism. He said that the ancients did not make more progress in science because “they did not, or could not, verify their theories” (PD 45). Furthermore, all that really distinguishes metaphysics from science in the modern era is that metaphysics lacks method and “well-grounded canons of research and criticism” (PD 366).