 So there is a categorical rational imperative of consistency, “ Be consistent in valuation and in thought and action” (Lewis 1946, 481) the basis of which is simply a datum of human nature, and a broader imperative of cogency or basing one’s beliefs on cogent reasoning from evidence (Lewis 1952b, 1952c), an imperative of prudence, “Be concerned about yourself in future and on the whole”, and an imperative of justice, “No rule of action is right except one which is right in all instances and therefore right for everyone” (Lewis 1946, 481–2). These principles are simply a priori explications of the rational or moral sense possessed by most humans. Certainly, this might be challenged. In any case, Lewis thinks that where that sense is lacking, argument for the principles is pointless, and he concludes AKV by claiming that “valuation is always a matter of empirical knowledge” but “what is right and what is just can never be determined by empirical facts alone” (Lewis 1946, 554).