Here was something which corresponded, however roughly, to the process by which practical people arrive at practical and responsible results. A railway manager who wishes to discover the highest rate of charges which his traffic will bear is not interested if he is told that the rate when fixed will have been due to the law that all men seek to obtain wealth with as little effort as possible, modified in its working by men's unwillingness to break an established business habit. He wants a method which, instead of merely providing him with a verbal 'explanation' of what has happened, will enable him to form a quantitative estimate of what under given circumstances will happen. He can, however, and, I believe, now often does, use the Jevonian method to work out definite results in half-pennies and tons from the intersection of plotted curves recording actual statistics of rates and traffic. Since Jevons's time the method which he initiated has been steadily extended; economic and statistical processes have become more nearly assimilated, and problems of fatigue or acquired skill, of family affection and personal thrift, of management by the _entrepreneur_ or the paid official, have been stated and argued in quantitative form. As Professor Marshall said the other day, _qualitative_ reasoning in economics is passing away and _quantitative_ reasoning is beginning to take its place.[43] [43] _Journal of Economics_, March 1907, pp. 7 and 8. 'What by chemical analogy may be called qualitative analysis has done the greater part of its work.... Much less progress has indeed been made towards the quantitative determination of the relative strength of different economic forces. That higher and more difficult task must wait upon the slow growth of thorough realistic statistics.' How far is a similar change of method possible in the discussion not of industrial and financial processes but of the structure and working of political institutions? It is of course easy to pick out political questions which can obviously be treated by quantitative methods. One may take, for instance, the problem of the best size for a debating hall, to be used, say, by the Federal Deliberative Assembly of the British Empire--assuming that the shape is already settled. The main elements of the problem are that the hall should be large enough to accommodate with dignity a number of members sufficient both for the representation of interests and the carrying out of committee work, and not too large for each member to listen without strain to a debate. The resultant size will represent a compromise among these elements, accommodating a number smaller than would be desirable if the need of representation and dignity alone were to be considered, and larger than it would be if the convenience of debate alone were considered.