Powell was an outspoken advocate of the constant uniformity of the laws of the material world. His views were liberal, and he was sympathetic to evolutionary theory long before Charles Darwin had revealed his ideas. He argued that science should not be placed next to scripture or the two approaches would conflict, and in his own version of Francis Bacon's dictum, contended that the book of God's works was separate from the book of God's word, claiming that moral and physical phenomena were completely independent.