1214 PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 28 
on the extent to which they restrict economic freedom. Thus one can 
compare only states of the economy that can be attained by instru- 
ments that are similar in their social impacts and this implies that 
constraints have to be brought into the picture from the outset for 
they describe the states that can be attained by means of a limited set 
of economic instruments. 
KooPMANS 
I am approaching my comment here in the same vein as Prof. 
DORFMAN. I am not addressing myself to the question whether so- 
ciety is or should be moving in the direction that Prof. FriscH’s 
paper indicates. Rather, for the purposes of the discussion, I am 
accepting his assumption that this is the direction, and speaking 
more technically to the point whether the particular layout and 
scheme of Prof. FriscH’s ideas is efficiently designed to achieve the 
purpose that he has in mind. I have really only two points that I 
would like to raise in this connection. One concerns the very strict 
separation of the determination of structure from the determination of 
preference. On this point I find my thinking to be somewhat related 
to that of Prof. ArLAIS. It would seem to me that the policy maker 
who is being interviewed in order to obtain a representation of his 
preferences will be neither able nor willing to be too specific about 
these preferences as long as he does not know what the implications 
of his indications are. He is likely to be pragmatic — not only a 
man who thinks abstractly about his own preferences. To stay in 
his position he must respond to pressures and perhaps even threats 
in order to be effective over a period of time. Even a man of great 
wisdom would still have to be aware of what he is expected to do 
by a number of groups who have ways of making their desires effec- 
tive. Therefore if he is presented by an econometrician with 
questions « what are your preferences » or « what is the form in 
which you would mould what you regard to be the preferences that 
should guide this planning », he may feel that he is being tricked 
even though without such intent. He is not an econometrician, and 
17] Frisch - pag. 18