224 PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 28 
diate or primary factors, and similarly all outputs produced should 
be assigned values; market prices when available. shadow prices 
when necessary. 
And, finally, if I have another 30 seconds, I should like to say 
something about the relationship of my thinking with Professor 
FriscH's, He asserts that one should begin with a social objective 
function or some measure of social welfare. My own contribution, 
if it be a contribution, is merely to set forth a way to discover 
certain aspects of the social welfare function. I do not feel that we 
can begin with it literally because at the beginning we do not know 
what it is. We must discover it by trying out proposals and seeing 
how the public and political organs react to them. In this way social 
preferences will be revealed, and a social welfare function will be 
discovered which can be used in designing and appraising invest- 
ment projects. 
51 Dorfman - pag. 38