1224 PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 2 
him and try to explain to him that his own way of solving his pro- 
blems, namely to jump out of the window, is not a good solution. 
The solution that is really good for him is of an entirely different 
nature. And I will try to help him find that solution. 
KOOPMANS 
There has been a misunderstanding, and I must express myself 
sufficiently clearly. I was not pleading that a policy maker's own 
idea of the structure be respected. I was pleading that when a policy 
maker is asked for his preferences, that he be given a chance to see 
the implications of confronting those preferences with the econome- 
trician’s model of the structure, so that he knows what is implied 
in the first indication of his preferences — and I think that in your 
answer to Prof. DorRFMAN you have already dealt with my point. 
FRISCH 
[ think this has cleared the question up perfectly. What Prof. 
KooPMANS says right now is just what I said a little while ago about 
the iterative process in discussion with the policy maker. But it is 
essential that the process be iterative in terms of complete optimal 
solutions. And if you are going to have any complete solution, you 
must start by a preference function, trying to lead the politicians 
mind completely away from his preconceived ideas of the structure. 
Prof. KooPMANS had a second point which is really covered, 1 
think, by what we have already discussed. « The whole thing must 
evolve by experiments ». I think that those were the words used 
by Prof. Koopmans, and of course my answer is absolutely « yes ». 
A third point raised by Prof. KooPMANS was about prices, how 
they can be used as means of implementations. He draws particular 
attention to the fact that you may have an economy with flip-flap 
>ffects of price changes. This is completely correct, And, as a matter 
of fact, I think that I have myself in some econometric papers poin- 
17] Frisch - pag. 28