There seems to us another error in Dr. Whately, which is worth noticing: he says," No conversion is employed for any logical purpose, unless it be illative ;" and he adds, " the reader must not suppose from the use of the word ' illative,' that this conversion is a process of reasoning: it is in fact only stating the same judgment in another form." Now if we say A is n, meaning that A is contained in B, it is a logical consequence or conclusion, though not a syllogistic one, that n is not contained in A. In this case then there can be no unlimited logical conversion of the proposition. If A is co-extensive with n, then B is co-extensive with A ; in which case there is a logical conversion. The laws of thought necessitate the non-conversion in the one case and the conversion in the other ; and if these are not logical conclusions, there is no such thing as a pure logic or reasoning.
It is generally said that logic teaches us to reason correctly, or that it shows the process which takes place in the mind when a man does reason correctly. It is however difficult to admit the accuracy of this statement. If a man reasons at all, in the strict logical sense, he reasons correctly. Language is seldom expressed in the form of syllogisms, and it is not usual to express, in any way, both the pro positions from which we deduce a conclusion. We generally express ourselves by way of a conclusion and one premiss. Now this being so, the suppressed premiss may always be discovered by somebody, though the speaker or writer may not always be able to discover his own suppressed premiss. The conclusion and one premiss being given, the suppressed premiss is also given, for the conclusion and the expressed premiss necessitate the proper suppressed premiss. They who say a man argues incorrectly, when he states a conclusion and one premiss only, assume that his suppressed premiss is not that suppressed pre miss which the two data require, but some other. But if some other, it is impossible that they can find it out, and therefore they cannot confute him. It is only because the suppressed premiss (perhaps not known to the speaker) pointed to by the data, is the real one, that we can confute the speaker. We show what the suppressed premiss is, and then we are in a condition to dispute it and to ask him for proof of it. A man then does reason correctly when he reasons by a con clusion and one expressed premiss. The syllogistic form shows what the premise must be, that is, it leads to the full interpretation of the speaker's meaning. But suppose a man expresses all the terms of a syllogism, and his syllogism is vicious, is it vicious because he reasons wrong, or because he has given a meaning to some of his terms which other people do not, or has altogether mistaken them / We think that his reasoning, as such, is and must be correct. His apprehension
may be and often is wrong. In this view, reasoning, as reasoning, is always correct reasoning. It has been objected to this by it friend, that many persons who are not familiar with logical considerations, on being asked whether, if every A is B, every is is also A, will admit this conversion to be true. It is then asked if, in admitting this, they reason correctly. The answer to this difficulty is furnished by the objector, who goes on to say, that if the person who admits this con version is asked the same question as to a material conversion, such as, every goose is an animal, he immediately perceives that he cannot say every animal is a goose. This shows that kis apprehension of the expression, every A is B, was incorrect, that is, he did not understand it, but took it to mean something different from what the person intended by it who put the question.
In argumentation the conclusions are the matters which are directly disputed ; but the suppressed proposition is generally the real matter in dispute, or the meaning of a term is the matter hi dispute. The use of logical forms consists in showing fully and explicitly what is expressed imperfectly and only implicitly in the common form of language ; and its use is not a bit the less because it neither teaches to reason nor convicts our reason of error. Its use is to indicate to us all the formal elements and conditions of dependent truth. It points out to us and leads us to the consideration of the several propositions which discourse contains, and from the consideration of the several propositions it leads to the terms, and there it leaves us.
The cause of this confusion between logic and metaphysic is obvious, and lies in the necessity which all men feel of a metaphysic of some kind or other. General terms and general propositions, the elements of every material syllogism, are deeply fixed in the mind long before its consciousness is awakened to the cognisance of the operations of the reason ; and in many minds this consciousness is never called into existence. Logicians clearly perceive the value of the syllogistic forms as an aid and a formal help in analysing the reasoning process in a given case : they also see or feel that the reasoning process in itself IS not knowledge, but they see that it is a means to knowledge. Its barrenness iu itself is confounded with its productive powers when exercised on a material, and hence they have come to confound its operating energies with its products; as if a man should confound his tools with that which is produced by his tools operating on his materials.