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

Most grown-up people get rid of the childish notion that whatever appears in print is true, but many cling to the equally absurd notion that the printing of a statement does give it some claim to dignity and credence. For the purposes of argumentation, let us here make this point emphatic: The mere fact that a statement appears in print lends not one atom to its value. Every assertion that is brought forward — though it may have been printed a thousand times and repeated a million times — must be challenged and tested before it can be regarded as trustworthy testimony of authority, — before it can be of any value as evidence.

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.

Formal debate is a kind of game. In the time limit, the order of speakers, the alternation of sides, the give and take of rebuttal, the fixed rules of conduct, the ethics of the contest, the qualifications for success, and the final awarding of victory, debate has much in common with tennis.