# Review of P. Coffey, “The Science of Logic”

Ludwig Wittgenstein

Review of P. Coffey, “The Science of Logic”

This digital edition is based on Ludwig Wittgenstein. "Review: P. Coffey, *The Science of Logic*." *The Cambridge Review*, vol. 34, no. 853, 6 Mar. 1913, p. 351. This original-language text is in the public domain in its country of origin and other countries and areas where the copyright term is the author's life plus 70 years or fewer.
Additionally, it is in the public domain in the United States, because it was published before 1 January 1927.

Ludwig Wittgenstein

Review: P. Coffey, *The Science of Logic*

*The Science of Logic: an inquiry into the principles of accurate thought and scientific method*. By P. Coffey, Ph.D. (Louvain), Professor of Logic and Metaphysics, Maynooth College. Longmans, Green & Co 1912.

In no branch of learning can an author disregard the results of honest research with so much impunity as he can in Philosophy and Logic. To this circumstance we owe the publication of such a book as Mr Coffey’s *Science of Logic*: and only as a typical example of the work of many logicians of to-day does this book deserve consideration. The author’s Logic is that of the scholastic philosophers, and he makes all their mistakes—of course with the usual references to Aristotle. (Aristotle, whose name is taken so much in vain by our logicians, would turn in his grave if he knew that so many Logicians know no more about Logic to-day than he did 2,000 years ago). The author has not taken the slightest notice of the great work of the modern mathematical logicians—work which has brought about an advance in Logic comparable only to that which made Astronomy out of Astrology, and Chemistry out of Alchemy.

Mr Coffey, like many logicians, draws great advantage from an unclear way of expressing himself; for if you cannot tell whether he means to say “Yes” or “No”, it is difficult to argue against him. However, even through his foggy expression, many grave mistakes can be recognised clearly enough; and I propose to give a list of some of the most striking ones, and would advise the student of Logic to trace these mistakes and their consequences in other books on Logic also. (The numbers in brackets indicate the pages of Mr Coffey’s book—volume I.—where a mistake occurs for the first time; the illustrative examples are my own).

- [36] The author believes that all propositions are of the subject-predicate form.
- [31] He believes that reality is changed by becoming an object of our thoughts.
- [6] He confounds the copula “is” with the word “is” expressing identity. (The word “is” has obviously different meanings in the propositions—
- “Twice two is four”
- and “Socrates is mortal.”)

- [46] He confounds things with the classes to which they belong. (A man is obviously something quite different from mankind.)
- [48] He confounds classes and complexes. (Mankind is a class whose elements are men; but a library is not a class whose elements are books, because books become parts of a library only by standing in certain spatial relations to one another—while classes are independent of the relations between their members.)
- [47] He confounds complexes and sums. (Two plus two is four, but four is not a complex of two and itself.)

This list of mistakes could be extended a good deal.

The worst of such books is that they prejudice sensible people against the study of Logic.

Ludwig Wittgenstein.