 Human perfectibility, for Jefferson, was a matter of improved efficiency of living, which implied not merely progress in the fields of human health and human productivity through discoveries and labor-saving inventions, but also and especially moral improvement. Moral improvement was much more important than exercise of rationality (e.g., TJ to Maria Cosway, 12 Oct. 1786). Pure rationality was a matter of humans abstracting from reality; moral sensibility was a matter of humans immersed in reality.