THE CHOICE OF UNITS
In this and the next three chapters we shall be occupied with an attempt to clear up certain perplexi ties which have no peculiar or exclusive relevance to the problems which it is our special purpose to examine . Thus these chapters are in the nature of a digression , which will prevent us for a time from pursuing our main theme . Their subject - matter is only discussed here because it does not happen to have been already treated elsewhere in a way which I find adequate to the needs of my own particular enquiry .
The three perplexities which most impeded my progress in writing this book , so that I could not express myself conveniently until I had found some solution for them , are : firstly , the choice of the units of quantity appropriate to the problems of the economic system as a whole ; secondly , the part played by expecta tion in economic analysis ; and , thirdly , the definition of income .
That the units , in terms of which economists com monly work , are unsatisfactory can be illustrated by the concepts of the National Dividend , the stock of real capital and the general price - level :
( i ) The National Dividend , as defined by Marshall