The theory and practice of argumentation and debate

by Victor Alvin Ketcham

2. The formation of trusts is an industrial evil.

3. Therefore the formation of trusts should be discouraged.

The exact phraseology has not been kept throughout the above line of reasoning, because seldom in any practical work do we find the exact words repeated except for emphasis. However, it requires the exercise of only ordinary ingenuity to follow precisely the entire reasoning processes involved in the foregoing argument.

An excellent example of the use of the deductive syllogism for the purpose of showing that an opponent’s deductive argument is unsound is the following extract from Lincoln’s reply to Douglas in the Fifth Joint Debate at Galesburg:

“In the second clause of the sixth article, I believe it is, of the Constitution of the United States we find the following language, ‘This Constitution and the laws of the United States which shall be made in pursuance thereof, and all the treaties made, or which shall be made under the authority of the United States, shall be the supreme law of the land; and the judges in every state shall be bound thereby, anything in the Constitution or laws of any state to the contrary notwithstanding.

“The essence of the Dred Scott case is compressed into the sentence which I will now read, ‘Now as we have already said in an earlier part of this opinion, upon a different point, the right of property in a slave is distinctly and expressly affirmed in the Constitution.’ I repeat it, ‘The right of property in a slave is distinctly expressed and affirmed in the Constitution.’ What is it to be ‘affirmed in the Constitution? Made firm in the Constitution,—so made that it cannot be separated from the Constitution without breaking the Constitution; durable as the Constitution, and part of the Constitution. Now remembering the provision of the Constitution which I have read; affirming that that instrument is the supreme law of the land; that the Judges of every state shall be bound by it, any law or constitution of any state to the contrary, notwithstanding; that the right of property in a slave is affirmed in that Constitution, is made, formed into, and cannot be separated from it without breaking it; durable as the instrument; part of the instrument; what follows as a short and even syllogistic argument from it? I think it follows, and I submit to the consideration of men capable of arguing whether as I state it, in syllogistic form, the argument has any faults in it? (1) Nothing in the constitution or laws of any state can destroy a right distinctly and expressly affirmed in the Constitution of the United States. (2) The right of property in a slave is distinctly and expressly affirmed in the Constitution of the United States. (3) Therefore nothing in the Constitution or laws of any state can destroy the right of property in a slave.

“I believe that no fault can be pointed out in that argument; assuming the truth of the premises, the conclusion, so far as I have capacity at all to understand it, follows inevitably. There is a fault in it as I think, but the fault is not in the reasoning; but the fault in fact is a fault of the premises. I believe that the right of property in a slave is not expressly and distinctly affirmed in the Constitution, and Judge Douglas thinks it is. I believe that the Supreme Court and the advocates of that decision may search in vain for the place in the Constitution where the right of property in a slave is distinctly and expressly affirmed. I say, therefore, that I think one of the premises is not true in fact.”

To give examples of all the forms in which deduction may be applied to argument is impossible. The foregoing examples are merely suggestive. They serve to make plain the practical use which can be made of this logical process. The student must master the underlying principles herein suggested and apply them to his own work.

III. The enthymeme.

An enthymeme is an incomplete syllogism. It is a syllogism in which only one or two of the statements are expressed. An example of an enthymeme is the following proposition, “The protective tariff should be abolished because it encourages the formation of trusts.” This is the form in which we most commonly encounter deductive reasoning. Seldom is the complete syllogism expressed. It therefore becomes our task to construct from this enthymeme a complete syllogism. Our first duty, then, is to find out what parts of the syllogism are contained in the enthymeme and then strive to supply the missing parts. Usually the major premise is omitted. This requires that it be supplied from a consideration of the minor premise and the conclusion. In almost all cases the conclusion is expressed. If it is not expressed it is clearly implied. This supplies the minor term (the thing about which something is said) and the major term (the thing that is said about it). From these two terms it is usually easy to find a middle term which will serve as a connecting link. The process of building syllogisms upon enthymemes is comparatively simple if the student will always find the conclusion and then divide it into the two terms of which it is composed.