Burden of Proof.  Every argument presupposes the opposite side.  Even when only one speaker appears his remarks always indicate the possibility of opposite views in the minds of some of the hearers.  The affirmative and negative are always present.  It is frequently asserted that the burden of proof is on the negative.  This is no more correct than the opposite statement would be.  The place of the burden of proof depends entirely upon the wording of the proposition and the statement it makes.  In general the burden of proof is upon the side which proposes any change of existing conditions, the side which supports innovations, which would introduce new methods.  With the passage of time the burden of proof may shift from one side to the other.  There was a time when the burden of proof was upon the advocates of woman suffrage; today it is undoubtedly upon the opponents.  At one period the opponents of the study of Latin and Greek had the burden of proof, now the supporters of such study have it.  Other topics upon which the burden of proof has shifted are popular election of Senators, prohibition, League of Nations, self-determination of small nations, the study of vocations, civics, and current topics in schools, an all-year school term, higher salaries for teachers, the benefits of labor unions, Americanization of the foreign born.

Evidence.  One of the best ways of proving a statement is by giving evidence of its truth.  Evidence is made up of facts which support any proposition.  In court a witness when giving testimony (evidence) is not allowed to give opinions or beliefs—­he is continually warned to offer only what he knows of the fact.  It is upon the facts marshaled before it that the jury is charged to render its verdict.

Direct Evidence.  Evidence may be of two kinds—­direct and indirect.  This second, especially in legal matters, is termed circumstantial evidence.  Direct evidence consists of facts that apply directly to the proposition under consideration.  If a man sees a street car passenger take a wallet from another man’s pocket and has him arrested at once and the wallet is found in his pocket, that constitutes direct evidence.  Outside criminal cases the same kind of assured testimony can be cited as direct evidence.

Circumstantial Evidence.  In most cases in court such direct evidence is the exception rather than the rule, for a man attempting crime would shun circumstances in which his crime would be witnessed.  Indirect evidence—­circumstantial evidence—­is much more usual.  It lacks the certainty of direct evidence, yet from the known facts presented it is often possible to secure almost the same certainty as from direct evidence.  In serious crimes, such as murder, juries are extremely cautious about convicting upon circumstantial evidence.  There are many chances of error in making chains of evidence.  In indirect evidence a group of facts is presented from which a conclusion is attempted.  Suppose