We have shown in Section 179 that one high school principal might believe that boys should be allowed to choose their own studies because he believed that they would not generally select the easy ones; while another principal would oppose free electives because he believes that boys would choose the less difficult studies.  The proposition that “The United States should retain its hold on the Philippines” involves conflicting theories of the function of this government.  So it will be found with many of our beliefs that either consciously or unconsciously they are based on general theories.  It is important in argument to know what these theories are, and especially to consider what may be the general theories of those whom we wish to convince.

+184.  Appeals to General Theory, Authority, and Maxims.+—­A successful argument in deductive form must be based upon principles and theories that the audience believes.  A minister in preaching to the members of his church may with success proceed by deductive methods, because the members believe the general principles upon which he bases his arguments.  But in addressing a mixed audience, many of whom are not church members, such an argument might not be convincing, because his hearers might deny the validity of the premises from which his conclusions were drawn.  In such a case he must either keep to general theories which his auditors do believe, or by inductive methods seek to prove the truth of the general principles themselves.

If in support of our view we quote the opinion of some one whom we believe competent to speak with weight and authority upon the question, we must remember that it will have weight with our audience only if they too look upon the person as an authority.  It proves nothing to a body of teachers to say that some educational expert believes as you do unless they have confidence in him as a man of sound judgment.  On the other hand, it may count against a proposition to show that it has not been endorsed by any one of importance or prominence.

In a similar way a maxim or proverb may be quoted in support of a proposition.  If a boy associates with bad company, we may offer the maxim, “Birds of a feather flock together,” in proof that he is probably bad too.  Such maxims or proverbs are brief statements of principles generally believed, and the use of them in an argument is in effect the presentation of a general theory in a form which appeals to the mind of the hearer and causes him to believe our proposition.

+185.  Argument by Inference.+—­The statement of a fact may be introduced into an argument, not because the fact itself applies directly to the proposition we wish to prove, but because it by inference suggests a general theory which does so apply.  Though the reader may not be conscious of it, the presence of this general theory may influence his decision even more than the explicit statement of the general theory would.