The words onus probandi mean the burden of proving. It may be useful to notice the cases in which this burden may rightfully fall upon you. In all cases when you attack a generally received opinion, you are bound to prove the unsoundness of that opinion. Sentiments which are universally acknowledged to be true, are seldom very minutely examined. There is no object in inquiring into the ground of a doctrine that no one ever denies. If you think any opinion of this kind is erroneous, you have a right to assail it; but you have no right to single out at a moment's warning any professed believer in that doctrine, and demand from him a reason for his creed. If you wish for controversy, you are bound to lead the attack. If you cannot do this, you had better hold your tongue.

If you advocate any kind of political or social reform, the onus probandi falls upon you. You are bound to show the advantages of the change. You have no right, in the first instance, to call upon your opponent to show that the proposed change would not be advantageous. Every new act of parliament is a change, and every member who brings forward a new bill is bound to show the advantages that would result from the adoption of the measures that he recommends.

If you offer a bill to your banker for discount, the onus • probandi falls upon you to prove that it is a good bill. If you cannot do this, he will be justified in refusing to discount it. You have no right to call upon him to prove that it is not a good one. So, if you give a bad character to any one, you are bound to prove the truth of your accusation. You have no right to call upon him to disprove the charge, and to assume it to be true if he cannot do so. The onus probandi in this as in the former case falls clearly on yourself.

Generally speaking, the onus probandi falls upon the advocate of the affirmative of any proposition. No man should be called upon to prove a negative. In practical questions, however, it is not always easy to state which side is properly the affirmative, as much will depend upon the wording of the sentence. But in all cases the assailant or challenger is bound to prove his own case; the onus probandi most unquestionably falls upon him. But a party

is not in all cases called upon to accept the challenge. And we will now notice the cases in which a challenge to controversy may be honourably declined. You are not bound to accept a challenge, to dispute upon a subject that you do not understand. If pressed for an opinion, you may fairly say, "I am not sufficiently acquainted with the matter to be able to offer any opinion on the subject." Nor are you bound to accept a challenge to disputation from a party who does not himself understand the question. We daily meet with people who think they know our business better than we do ourselves, and who are anxious to dispute with us upon the most knotty points of our profession. In this case we had better answer one question by asking another, and if we have nothing to contend against but simple ignorance, without conceit or obstinacy, we may, peradventure, by the adoption of Socra tical interrogations, lead our pugnacious friend into a better knowledge of the subject. When Nathanael asked, "Can any good thing come out of Nazareth?" Philip did not engage in controversy on the question, but merely replied, "Come and see."

SECTION III.

CONVERSATIONAL REASONING.

I say

By conversational reasoning, I mean that kind of reasoning which is employed chiefly in conversation. chiefly, for there is no kind of reasoning that is employed exclusively in conversation, nor is conversational reasoning confined to only one kind. But all kinds of reasoning, when employed in conversation, are employed in a different manner as to the form or mode of expression, than when employed in books or in speeches. It is impossible to describe all these forms. Every man will express his reasons in conversation in a way of his own, according to his constitutional temperament, his education, his temper at the time, the occasion, or the manners of the society in 'which he is accustomed to move. You may therefore

improve your knowledge daily by merely observing the conversation of your friends. You will find examples of conversational reasoning in the fifteenth chapter of the first book of Samuel, and in the eighth chapter of the Gospel according to St. John.

1. The language and form of conversational reasoning.

This is chiefly by enthymemes. I wish I had a good English word to substitute for the Greek word enthymeme -it signifies, from the mind. Reasoning by enthymemes therefore means reasoning from the mind-reasoning as you think, or talk, or write, in the ordinary affairs of life. You have heard of a character in a French play, who was surprised to learn that he had been talking prose for fifty years without knowing it. He might have made the same observation respecting enthymemes. Whenever you have given a reason, you have spoken an enthymeme. If you observe to a friend, "It is a fine day," that is a description. If you ask, "Is it going to be wet?" that is an interrogation. If you say, "I shall take my umbrella, for I think it will rain," that is an enthymeme.

Enthymemes are treated of largely in Aristotle's Rhetoric. The following is the substance of his doctrine respecting them. An enthymeme bears the same relation to rhetoric as a syllogism to logic. It is composed of a sentence and a reason. A sentence is a general proposition concerning those things which are to be desired, or avoided, and it bears the same relation to an enthymeme as any proposition to a syllogism. And therefore a sentence, if a reason be rendered, becomes a conclusion, and both together make an enthymeme. The following is an example given by Aristotle: "To be over-learned produces effeminacy and envy. Therefore, he that is wise, will not suffer his children to be over-learned." The form of this enthymeme may be reversed thus:- "A wise man will not suffer his children to be over-learned, because too much learning produces effeminacy and envy."

The Rev. John Huyshe, M.A. of Brazenose College, Oxford, in a Treatise on Logic, intended to assist those who wish to study Aldrich's Logic, in order to pass their

examination in the Oxford schools, has thus treated of enthymemes

"The enthymeme is a defective syllogism, which consists of one premiss and a conclusion; e.g.

Diamonds are jewels; they are therefore valuable.' 'God is a spirit; therefore he is eternal.'

"An enthymeme may easily be reduced to a regular syllogistic form; for since the conclusion and one premiss are given, the three terms may be known, and the omitted premiss may be supplied thus, in the above example, the major, All jewels are valuable,' is omitted, and, if supplied, the syllogism will be regular, thus:

"In both these examples, the major premiss is suppressed; for, as was before observed, the major premiss is, generally speaking, some universal and incontrovertible principle, which is so evident that it is left to the hearer's judgment; but the minor premiss is most commonly expressed, because it has more particular reference to the question which is to be proved.

"In common discourse the usual mode of expressing an argument is by means of the enthymeme; it being unnecessary to adduce both the premises, when one is so evident that it may very fairly be left to the hearer's judgment; e.g.

"When we find a book quoted, or referred to by an ancient author, we are entitled to conclude that it was read and received in the age and country in which that author lived.' This sentence is an enthymeme, in which the major premiss is suppressed, but which may easily be supplied as follows: Every book quoted, or referred to by an ancient author, must have been read and received in the age and country in which that author lived.' The sentence may thus be reduced to a regular syllogism in Barbara: this may be effected in most enthymemes without much difficulty, whether their conclusions be negative or affirmative.

Although the major premiss is generally suppressed in most enthymemes, yet there are some enthymemes in which the minor premiss is found to be omitted: this may happen when the minor premiss is very evident, or when much stress is meant to be laid upon the major; e. g. Every tyrannical king deserves to be deposed by his subjects; therefore Nero deserved to be deposed by

the Romans. The minor premiss, which is suppressed, may be thus supplied:

'Nero was a tyrannical king:'

and thus the argument is reduced to the regular syllogistic form. "An enthymeme is sometimes condensed into one sentence, which is called an enthymematic sentence; viz. when the premiss is united in one proposition with the conclusion; e.g. All machines, being of human manufacture, are liable to imperfections. This argument may be thus expanded into a regular syllogism:

All things of human manufacture are liable to imperfections; '

All machines are of human manufacture: '

therefore, They are liable to imperfections.' -Huyshe's Treatise on Logic.

The following are examples of enthymemes given by

Mr. Hill.

66

The human soul is immaterial, consequently it is immortal. "We enjoy a greater degree of political liberty than any civilized people on earth, and therefore have no excuse for a seditious disposition.

"The power of ridicule is a dangerous faculty, since it tempts its possessor to find fault unjustly, and to distress some for the gratification of others.

The study of mathematics is essential to a complete course of education, because it induces a habit of close and regular reasoning.

"Hard substances may be elastic, for ivory is both hard and elastic."

The following are examples of enthymematic sen

tences:

"The example of Virgil shows that even a great poet may be seduced into some faults by the practice of imitation.

"The apparent insufficiency of every individual to his own happiness or safety, compels us to seek from one another assistance and support.

"Should such a man as I flee?

"Real learning is too valuable a thing to be within the grasp of the idle.

"I ask your lordships, whether Parliament will be in a state to transact public business, or be attended by a sufficient number of members, while engaged in preparing for a public election.”— Hill's Logic.