It is not easy to phrase the proposition so that it shall mean precisely what we wish to argue; so that it shall include the whole matter at issue, n… - William Trufant Foster

The reference to the source of authority should be definite. Such vague phrases as the following, common though they are, are worthless as proof : —

One of the early presidents of Harvard College wrote a dissertation on the question, "Whether angels speak any language; if so, whether it is Hebrew." Much futile discussion on such questions has at various times brought debating into ill repute. A question should offer something more than an ingenious exercise; it should offer the chance of arriving at some conclusion regarded by the particular audience or disputants as of some practical importance. It should be discarded if, like the proposition, "The pen is mightier than the sword/' it offers no possibility of arriving at reasonably sound conclusions through the process of argument.

The double reservoir at the top shows the amount of money in the hands of individuals and available for expenditure in consumption. This is what we have previously called the consumers' fund. The reservoir is divided into two parts in order graphically to represent the fact that a large part of the money received by individuals is income, most of which is spent in consumption; while a smaller part is money received from the sale of real estate, bonds and stocks, most of which is reinvested. The two parts of the reservoir, however, are connected with pipes, in order to take account of the fact that some income is invested and some money received from the sale of securities is spent in consumption. These connecting pipes are important. We must bear in mind that they are always partly, and never wholly, clogged. By their aid, we may visualize the fact that we have no means of knowing how much of the consumers' fund actually will be spent in consumption in any given period of time.