Reference request: Oldest books on logic with unsolved exercises? Per the title, what are some of the oldest books on logic out there with unsolved exercises? Maybe there are some hidden gems from before the 20th century out there.
Update: Doesn't have to be mathematical logic per se. I mean logic at large.
 A: I have not succeeded in going back much more than 50 years for a textbook on mathematical logic with excercises:


*

*Introduction
to Mathematical Logic, by Elliott Mendelson (1964)

*Mathematical
Logic, by Joseph Shoenfield (1967)

*Mathematical
Logic: A First Course, by Joel Robbin (1969)
one exercise from the 1964 book

A: In Symbolic Logic by Lewis Carroll (1896), most of the exercises have solutions, but there are four problems in the appendix (pp. 185-188) that do not.  Carroll writes "I shall be very glad to receive, from any Reader, who thinks he has solved any one of them, what he conceives to be its complete Conclusion."
(These four problems were apparently meant as a preview of Part II of the work, which Carroll did not complete before his death in 1898.  It seems a version was eventually published in 1977.)
A: The update to the question now asks for "logic at large" -- rather than specifically mathematical logic. Then one can go back to before the 20th century, as in:


*

*Studies and exercises in formal logic, J.N.Keynes, 1884.

*Questions and exercises in elementary logic, deductive and
inductive, W.H. Forbes and D. Hird, 1875.

*Exercises in logic, J.T. Gray, 1845.

*Logic; or, The art of reasoning simplified. With exercises on a variety of interesting topics, to guide and develope the reasoning powers of the youthful inquirer after truth, S.E. Parker, 1837.

one exercise from Keynes
A: What about Hilbert/Ackermann: Grundzüge der Theoretischen Logik (1958), 4th edition. This edition definitely has unsolved exercises. I have no access to former editions. The first one is from 1928. There is no remark in the 1958 edition that excercises have been added.
