Lewis tries to understand Gaius and Titius’s system of ethics. He concludes that they regard instinct as the source of values, but, to Lewis, instinct is an inadequate source of values. Firstly, there are different instincts in man that contradict each other, and secondly, instinct does not encourage us to plan for the future. Neither can we find the basis of moral values in factual propositions, because we cannot logically pass from these propositions to the necessity of doing certain actions. Instead, moral values come from the Tao, a Chinese philosophical term. The Tao is the basic ground of all moral values. In rejecting it, we reject all value. Even the rational or biological values advocated by Gaius and Titius are derived in some sense from the Tao even if they do not acknowledge the connection. Lewis maintains that a half-hearted rejection of some values in favor of others will not work, because the Tao is a unified and integrated system.