Hayek on The Value of Science

Hayek in Rules and Order:

There is another related misconception about the aim and power of science which it will be useful also to mention at this point.  This is the belief that science is concerned exclusively with what exists and not with what could be.  But the value of science consists largely in telling us what would happen if some facts were different from what they are.  All the statements of theoretical science have the form of 'if  . . . , then . . .' statements, and they are interesting mainly in so far as the conditions we insert in the 'if' clause are different from those that actually exist. . . . the chief value of all science is to tell us what the consequences would be if conditions were in some respects made different from what they are. . . . Fruitful social science must be very largely a study of what is not: a construction of hypothetical models of possible worlds which might exist if some of the alterable conditions were made different.  We need a scientific theory chiefly to tell us what would be the effects if some conditions were as they have never been before.  All scientific knowledge is knowledge not of particular facts but of hypotheses which have so far withstood systematic attempts at refuting them. (p. 17)