Charles Leslie Stevenson var en av 1900-talets stora moralfilosofer: en av emotivismens företrädare och en föregångare till dess moderna variant, expressivismen. Nå, här vill jag lyfta fram Stevensons syn på vetenskap och moral. Sam Harris hävdar i The Moral Landscape: How Science Can Determine Human Values att man med vetenskap kan fastslå vilken den korrekta moralen är. Vad hade Stevenson att säga om sådana tankegångar? Två citat är upplysande:

If the men come to agree in belief about all the factual matters they have considered, and if they continue to have divergent aims in spite of this … they will still have an ethical issue that is unresolved. But if they come to agree [in attitude], they will have brought their ethical issue to an end; and this will be so even though various beliefs … still remain debatable. Both men may conclude that these remaining beliefs, no matter how they are later settled, will have no decisive effect on their attitudes.

(S)cientific methods cannot guarantee the definite role in the so-called normative sciences that they may have in the natural sciences. Apart from a heuristic assumption to the contrary, it is possible that the growth of scientific knowledge may leave many disputes about values permanently unsolved. … For the same reason I conclude that normative ethics is not a branch of any science. It deliberately deals with a type of disagreement that science deliberately avoids. … Insofar as normative ethics draws from the sciences, in order to change attitudes via changing people’s beliefs, it draws from all the sciences; but a moralist’s peculiar aim—that of redirecting attitudes—is a type of activity, rather than knowledge, and falls within no science. Science may study that activity and may help indirectly to forward it; but it is not identical with that activity.

Detta synes mig vara helt och hållet korrekt — ergo har Harris fel. Däremot kan förstås vetenskapen bidra med att hjälpa oss förstå hur världen är konstituterad, vilket kan påverka ställningstaganden i olika frågor. Se även vad Bertrand Russell, Isaiah Berlin och A.J. Ayer hade att säga i denna fråga