I have now reached a stage in the argument where I have to choose between being too definite or being too vague. If I set forth a concrete proposal in all its particulars, I expose myself to a hundred criticisms on points not essential to the principle of the plan. If I go further in the use of figures for illustration, I am involved more and more in guess-work; and I run the risk of getting the reader bogged in details which may be inaccurate and could certainly be amended without injury to the main fabric. Yet if I restrict myself to generalities, I do not give the reader enough to bite on; and am in fact shirking the issue, since the size, the order of magnitude, of the factors involved is not an irrelevant detail.