SECTION IV. ANTECEDENT PROBABILITY, EXAMPLE, SIGN. Three classes The classification of arguments as deductive and inductive, though primarily useful to a student of logic, is not without value to a student of rhetoric, since it of arguments. helps him to test the validity of his own or another's reasoning. A classification more convenient for our purposes is that which distinguishes arguments according to the sources from which they come, - according as they are derived (1) from the relation of cause to effect, (2) from the resemblance which persons or things bear to one another in certain particulars or under certain aspects, (3) from the association of ideas. Arguments of the first class are called arguments from ANTECEDENT PROBABILITY; those of the second class, arguments from EXAMPLE; those of the third class, arguments from SIGN. antecedent No form of argument is in more frequent use than the Argument from argument from ANTECEDENT PROBABILITY. probability. This argument is employed in reasoning either from the present to the future, or from the past to the present or the future. We argue from antecedent probability that the superior skill which has enabled a base-ball nine to win successive victories will enable it to win again; that a habit (bad or good) once formed will continue; that a national peculiarity which has been shown in military affairs will be shown in civil affairs when opportunity arises. Shrewd observers of the condition of things in France in the middle of the eighteenth century argued from antecedent probability that a revolution was at hand. Statesmen who had studied the English character and the course of events in the American colonies anticipated, long before (antecedently to) the actual struggle, that there would be a conflict between those colonies and the mother country. A few far-seeing Americans anticipated before Fort Sumter was fired upon that there would be an attempt to separate the slave States from the free. Any one who knew the Puritan character might have foreseen very early in the seventeenth century that if the Puritans came into power they would close the theatres. A student of English literature might have foreseen that the Elizabethan era would be characterized by the predominance of the drama; and this general probability would have been strengthened by the special probability furnished by Queen Elizabeth's liking for the theatre combined with her love of the classics. In each of these cases, the argument from antecedent probability is a means of inferring what is likely to be from what is or from what has been. The argument rests on the generally-accepted belief that certain causes tend to produce certain effects, that what Matthew Arnold calls "the stream of tendency" will continue to flow in the direction once taken. The argument from antecedent probability is also used as a means of accounting for what has already happened. A reasoner, assuming a proposition to be true, tries to show how it probably came to be true. If a loaf of bread which had been within reach of a starving man were to disappear, an argument that the starving man was the thief might be based on knowledge of the fact that he was starving; for experience shows that a starving man is likely to lay hands on anything eatable that comes in his way. This probability existed before the disappearance of the loaf: the cause was in operation before the occurrence of that which had to be accounted for. In accounting, then, for what has already happened, as well as in inferring what is likely to happen, the argument rests on the probability that certain. causes will produce certain effects. An argument of this class is used by Mr. Galton to prove that there was a larger proportion of color-blind men among the original Quakers than among the people from whom they separated themselves: "I may take this opportunity of remarking on the well-known hereditary character of colour blindness in connection with the fact, that it is nearly twice as prevalent among the Quakers as among the rest of the community, the proportions being as 5.9 to 3.5 per cent. We might have expected an even larger ratio. Nearly every Quaker is descended on both sides solely from members of a group of men and women who segregated themselves from the rest of the world five or six generations ago; one of their strongest opinions being that the fine arts were worldly snares, and their most conspicuous practice being to dress in drabs. A born artist could never have consented to separate himself from his fellows on such grounds; he would have felt the profession of those opinions and their accompanying practices to be a treason to his æsthetic nature. Consequently few of the original stock of Quakers are likely to have had the temperament that is associated with a love for colour, and it is in consequence most reasonable to believe that a larger proportion of colour-blind men would have been found among them than among the rest of the population.” 1 The argument from antecedent probability is used by the man of science when he frames a hypothcedent proba- esis to account for a phenomenon hitherto unexplained. It was by this argument that Newton accounted for the fall of an apple from a Use of ante bility by science. 1 Francis Galton: Inquiries into Human Faculty and its Develop ment; Unconsciousness of Peculiarities. tree when he framed the hypothesis which has led to what we call the law of gravitation. It was by this argument that Darwin accounted for certain observed facts when he framed the hypothesis that "natural selection" explains "the survival of the fittest." It was an argument of this sort which led to the discovery of argon. The fact that the nitrogen obtained from chemical compounds is lighter than atmospheric nitrogen raised an antecedent probability that the latter contained some element other than nitrogen. This probability was strengthened by a series of experiments that resulted in the separation from atmospheric nitrogen of a gas hitherto unknown, which the discoverer has named argon.1 Further evidence was derived from the fact that similar experiments with chemical nitrogen yielded only a very small amount of the new gas, so small that it might have leaked in from the atmosphere. but Use of antecedent probability in fiction. The writer of fiction uses the argument from antecedent probability in the construction of a story. He may bring any characters he chooses upon the stage; those whom he does bring there should be natural, that is, they should talk and act as such characters would be likely to do. He may invent any series of events; but he should take care not flagrantly to violate probabilities familiar to his readers. He should prefer an impossibility which seems probable to a probability which seems impossible; 2 for he aims at universal, not at particular, truth.3 The necessity of paying attention to antecedent probability in the conduct of a fictitious narrative has been recognized by all great novelists. It was recognized by 1 From a privative, and ěpyov, work. 2 See Aristotle: Poet., xxv. xvii. 3 Ibid., ix. iii. Richardson when, in spite of numerous protests, he let Clarissa Harlowe die; the fact that his readers foreboded the death of Clarissa tended to prove that the course of the story would naturally lead to her death. It was recognized by Dickens when he paid no attention to the general demand that little Nell should not die. It was recognized by Hawthorne when he wrote that it was impossible to end "The Blithedale Romance" in any way but that dreaded by his readers. What is true of all fiction is especially true of so-called "novels with a purpose,” — novels written to establish a certain proposition. They succeed or fail according as they do or do not square with the facts of human experiFiction can help us more clearly to understand what we believe or more firmly to hold our beliefs; but, the premisses of fiction being arbitrarily selected, its conclusions can be binding upon those only who admit the premisses. ence. In every piece of reasoning some argument from antecedent probability should be adduced if possible; for it is difficult to create a belief in the existence of Need of argu ment from antecedent anything that cannot be accounted for. It is probability. difficult, for example, to convict an accused person unless a sufficient motive can be discovered for the crime with which he is charged. In the famous trial of Levi and Laban Kenniston, indicted for highway robbery on the person of Major Goodridge, Webster based his argument for the defence on the hypothesis that Goodridge robbed himself. The main difficulty with this hypothesis was that of assigning a sufficient motive for such an act. This difficulty is apparent in Webster's argument: "It is next to be considered whether the prosecutor's story is either natural or consistent. But, on the threshold of the inquiry, |