PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 20 
some other country. It is possible to make models which are rea- 
listic in the sense of Professor STONE but which cannot be verified 
in the U.S.A., because there is not much of central planning there, 
but which are capable of being verified in the U.S.S.R., or which 
may find great opportunities for experimentation in a centrally plan- 
ned country like U.S.S.R. 
To sum up, I suggest that it would be useful to go into the 
question of terminology at one stage, to identify the hierarchical 
levels of multi-dimensional analysis. Professor FRISCH may be able 
to think of suitable words. An appropriate terminology would be of 
help in fitting « macro » or « micro » models at different levels into 
a global frame of the world as a whole, and to delimit different 
domains of interest (also of a multi-dimensional character, and cover- 
ing, as necessary, both social and political aspects) to suit the purpose 
in view. 
WoLD 
It is most appropriate that Prof. MAHALANOBIS has given us some 
broad indications towards a general frame of reference for our Study 
Week. Prof. STONE’s excellent paper gave a very good start in this 
direction, and Prof. MAHALANOBIS has now emphasized the regional 
view of the globe. I would like to take up another basic aspect, 
also with a view to clarify fundamental ideas, namely the general 
philosophy of model building. The need for a broad consensus about 
views and terminology is here so much the more pressing, as the lite- 
rature of professional philosophy leaves much to be desired in this 
respect. The situation is somewhat paradoxical, for in almost any 
creatise of philosophy of science we find a laudable introductory 
statement to the effect that the area of the treatise is the procedures 
and methods in current use in the many branches of science, the 
purpose of philosophy of science being to study and assess the general 
principles of scientific inference; on the other hand it is clear that 
although the approach of model building by and large is all pervading 
'1] Stone - pag. 90