## Thursday, March 30, 2017

Modus ponensis a classically valid inference pattern. Its classical truth table shows that there is no case in which the premises are true and the conclusion is untrue. (Note the use of the word 'untrue' here rather than 'false.' In classical logic, the only value that is untrue is false, but that is not the case in multi-valued logic.)

Task: Draw complete truth tables formodus ponensfor both Bochvar's and Kleene's versions of three-valued logic (in the slides, policy 1 and policy 2 respectively.) Then answer the following questions:

1. Do either of these systems preserve the validity ofmodus ponensas defined above?

2. What does your answer suggest about the relative desirability of these systems?

## Wednesday, March 29, 2017

## Tuesday, March 28, 2017

Also, I posted full solution to Monday's homework on the schedule page. This contains the answers to a few problems I skipped because I wasn't completely sure how they should be evaluated. I have confirmed these solution and they are highlighted in blue. The rationales are straightforward and you should familiarize yourself with them. Ask questions Wednesday if you don't understand them.

## Tuesday, March 21, 2017

## Wednesday, March 15, 2017

I will assign homework on the semantics of free logic by Wednesday next week, due Monday the 27th when we return from spring break. Also, I have decided to push the next text back. It is now scheduled for April 17th.

## Monday, March 13, 2017

Wednesday we will work the remaining problems from today's homework. Please turn in numbers 9 and 11. The second half of the period we will begin talking about Meinongian free logic.

## Friday, March 10, 2017

## Thursday, March 9, 2017

## Monday, March 6, 2017

## Friday, March 3, 2017

See below for Monday homework.

Grades for test 1 have been posted to SacCT. These reflect a curve of 2 points, which produced a mean score of 17.5 = 70%. Your returned copy will only show your original score. Be sure to check my addition and also that your score in SacCT is 2 points higher than the score on your test.

Now is a good time to review the syllabus and refresh your memory on the impact of this test and ways to recover if you have done poorly. Note that the deadline on one of those ways, participating in the Nammour Symposium Student Contest, is fast approaching. Check the department Facebook link for the most recent announcements.

Grades for test 1 have been posted to SacCT. These reflect a curve of 2 points, which produced a mean score of 17.5 = 70%. Your returned copy will only show your original score. Be sure to check my addition and also that your score in SacCT is 2 points higher than the score on your test.

Now is a good time to review the syllabus and refresh your memory on the impact of this test and ways to recover if you have done poorly. Note that the deadline on one of those ways, participating in the Nammour Symposium Student Contest, is fast approaching. Check the department Facebook link for the most recent announcements.

This is the turn-in homework for Monday:

In the semantics of Leibnizian modal logic, the following proposition is a necessary truth.

□(P → Q) → (□P → □Q)It says that "If it is necessarily the case that if P then Q, then if it is necessarily the case that P, then it is necessarily the case that Q."

Use Leibniz's notion of possible worlds to explain in English why this should be a necessary truth.

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