## Symbolic logic by Lewis Carroll

Symbolic logic by Lewis Carroll |

**From introduction:**

**The chief alterations, in this Edition, have been made in the Chapter on ' Classification ' (pp. 2, 3) and the Chapter on 'Propositions of Existence' (pp, 12, 13).**

**In the first of these, I have adopted a new definition of the Process, which enables me to regard the whole Universe as a ' Class,' and thus to dispense with the very awkward phrase ' a Set of Things.' In the second,**

I have adopted a new 'normal form,' in which the Class, whose existence is affirmed or denied, is regarded as the Predicate, instead of the Subject, of the Proposition, thus evading a very subtle difficulty which besets the other form.

these subtle difficulties seem to lie at the root of every Tree of Knowledge, and they are far more hopeless to grapple with than any that occur in its higher branches. For example, the difficulties of the Forty-Seventh Proposition of Euclid are mere child's play compared with the mental torture endured in the effort to think out the essential nature of a straight Line. And, in the present work, the difficulties of the " 5 Liars" Problem, at p. 188, are " trifles, light as air," compared with the bewildering question '' What is a Thing? " Besides these alterations,

I have corrected several misprints, some of which have been pointed out to me by friends but none of my critics has been sharp-eyed enough to detect the splendid misprint at p. 109, where the following Trio of Propositions is proposed as a Syllogism: Kind friends have tried their best, with a really touching confidence in the infallibility of author and printer, to make sense of this hopeless jumble; and no suspicion has crossed their innocent minds ("For they suspected harm from none, They were themselves so good ") that the second Premiss has wandered in here from the opposite page, and has displaced the lawful occupant, viz. "

No banker is imprudent." Lastly, I have corrected one terrible mistake of my own, pointed out to me by a logical friend, who wrote that he had twice worked out the "5 Liars" Problem, and brought out the result " no solution." And it was, even so, I had to confess (of course in the appropriate attitude, prostrate, prone, and with ashes on my head). However, by transposing two words, I have set things right, and can now guarantee, to any Reader bold enough to attempt the Problem, that there is a solution if only he can find it! In conclusion,

let me point out that even those, who are obliged to study FGrmal Logic, to be able to answer Examination-Papers in that subject, will find the study of SyinhoUc Logic most helpful for this purpose, in throwing light upon many of the obscurities with which Formal Logic abounds, and in furnishing a delightfully easy method of testing the results arrived at by the cumbrous processes which Formal Logic enforces upon its votaries.

This is, I believe, the very first attempt (except for my own little book. The Game of Logic, published in 1886, a very incomplete performance) that has been made to this fascinating subject. It has cost me years of hard work: but if it should prove, as I hope it may, to be of real .service to the young, and to be taken up, in High Schools and in private families, as a valuable addition to their stock of healthful mental recreations, such a result would more than repay ten times the labour that I have expended on it.

The Learner, who wishes to try the question y^wV^?/, whether this little book does, or does not, supply the materials for a most interesting mental recreation, is earnestly advised to adopt the following Rules: