PHL111 Valid Reasoning, Past Assignments

Past Assignments
31 August
Reading: Read chapter 1 of CIL.

2 September
Practice: Hand in at the beginning of class your answers to problems 1-5 at the end of chapter 1. Each of these problems asks you to come up with 5 examples; to make the homework shorter, for each problem just come up with 2 examples. Handwritten is acceptable (for many of our later homeworks there are special symbols or tables and it is too much work to try to type them).
7 September
Reading: Read chapter 2 of the book.
12 September
Practice: Complete problems 5 and 6 at the end of chapter 2.
14 September
Reading: Read chapter 3 of the book.

Here is an alternative view of arguments (especially in the minute starting around 1:40 and following); one closer to the colloquial use of the word "argument"--but different than our technical use of the word.
16 September
Read: chapter 4 of CIL.

19 September
Homework: do problems 1a, 1b, 2a, 2b, and 3 of chapter 3.
23 September
NOTE: I have an unexpected emergency, and must cancel my offices hours this afternoon. Write me and we'll find time for you Monday if you need to see me.

Alternative homework: Some people found the last homework confusing and did not manage to complete it correctly. If you want to try a redo, or a first/late do, you can instead do the following: chapter 3 problems problems 1c, 1d, 2c, 2d, and 3.

Please note: I've been informed that the book does not load correctly on a phone! Sorry. Be sure you read it on a computer screen in order to see the truth tables correctly!
26 September
Practice: Do problems 1 and 4 of chapter 4. This is nine proofs, but they are short, and a good block of practice will help you become familiar and comfortable with direct derivations.

Reading: Read chapter 5 of the book.
30 September
Practice: Of chapter 5, do problems 2a, 2b, 2d, 2e; and 3a, 3b, 3c, 3d.

NOTE: "Direct derivation" is another way of saying "direct proof." So if I ask for a direct derivation I am asking for a direct proof (and not a truth table). Thanks!

Our slides from last class as a pdf.

Here is a printable version of chapter 10. Print it and keep it with you.

I apologize, but I have a conflict with my office hours on this day and will not be able to hold my office hours. Email me and we can meet another time if you need to talk with me.
3 October
No class.
5 October
Read: chapter 6 of A Concise Introduction to Logic.
6 October
There is a philosophy talk on Mind, Metaphysics, and the Future, by Pete Mandik. It's in our classroom, from 4:00 to 5:00 pm. This will be a fun talk and I will give extracredit to encourage you to come (sign up in the back of the room to get the extra credit, which will be worth the equivalent of a homework).
7 October
Practice: Of chapter 5, do problem 7; of chapter 6 do problem 1.

NOTE: my office hours must start at 2:00 today, but they can run as late as you would like!
11 October
I will have office hours from 1 to 3 pm. Please note that I cannot have office hours on Friday, and Wednesday is our holiday, so this would be a good time to see me this week if you need me. Try out the next homework now so you know if you need some help.
12 October
No class.
14 October
Practice: due at the beginning of class. From chapter 6 do problems 2b, 2d, and 4.

I apologize but I have a conflict this afternoon and cannot have my office hours at 1:30. Please contact me should you need to see me.
17 October
I'm sick!

Some of you asked me for practice problems. Here are a few. I will post answers later. These include "or", but that's good because we haven't practiced that yet.
    Here are some practice translations. Make a key and translate the sentences.

  1. Neither Fry nor Bender eat Bachelor Chow.
  2. If either Fry or Bender eat Bachelor Chow, then Fry will drink Slurm.
  3. Bender eats bachelor chow only if Fry drinks slurm.
  4. Bender eats bachelor chow if Fry drinks slurm.
  5. Either Bender doesn't eat Bachelor Chow or Fry does.

    For these next two problems, create a key, translate the passage, and prove the argument is valid using a proof.

  6. Either the Professor Plum or Miss Scarlet killed Colonel Mustard. If Professor Plum killed Colonel Mustard, then Professor Plum was in the kitchen. If Miss Scarlet killed Colonel Mustard, then she was in the drawing room. If Miss Scarlet was in the drawing room, then she was wearing boots. But Miss Scarlet was not wearing boots. So, Professor Plum killed the Colonel.
  7. Either Mrs. White or Mrs. Peacock stole the diamonds. If Mrs. Peacock stole the diamonds, then she was in the billiards room. But if Mrs. Peacock was in the library, then she was not in the billiards room. Therefore, if Mrs. Peacock was in the library, Mrs. White stole the diamond.
Here are my answers, without the proofs yet.

Here is a proof for 6, and Here is a proof for 7.
19 October
In addition to the practice problems of 17 October, here are some more. Try to prove the following theorems.
  1. (((P ^ Q) → R) → (P → (Q → R)))
  2. ((P → (Q → R)) → (Q → (P → R)))
  3. (((P → (Q → R)) ^ Q) → (P → R))
Here is a proof for 1, and Here is a proof for 2, and Here is a proof for 3.

Extra credit. I'll give extra points to anyone who can do the following. You can work in teams; just let me know everyone in your team. Keep it to fewer than 6 people per team, please. Hand it in on Friday at the beginning of class.

Translate the following passage into propositional logic. Prove the argument is valid using a direct proof. (This is review of older stuff, since it does not require a conditional derivation.)
If Miss Scarlet killed the colonel, then she was in the billiards room. Professor Plum has chalk on his hands. Miss Scarlet has chalk on her hands, and she shook hands with Professor Plum. If Miss Scarlet has chalk on her hands, then if she shook hands with Professor Plum, then she was not in the billiards room. If Professor Plum did not kill the colonel, then Miss Scarlet killed the colonel. We deduce that Professor Plum killed the Colonel.
24 October
Test 1 in class. Specific topics include: meaning of each of the connectives (that is, the defining truth table for the connective); direct and conditional derivations; translations; meaning of valid, sound, tautology, theorem, contingent sentence, and contradictory sentence; using truth tables to determine the meanning of a complex sentence; using truth tables to perform a semantic check of an argument.
26 October
Read chapter 8.

In case anyone is interested, the College of Liberal Arts and Sciences is having its Brown Bag lunch conversation on "Election 2016: Beyond the Soundbite," a discussion on what has been left out of the national conversations during this election cycle. The topics are: "A Vision of Other Economies" (me), "The Aftermath of Mass Shootings: The Gun Debate and National Crime Statistics" (Jacklyn Schildkraut), and "A Defense of Intellectualism and Science" (Shashi Kanbur). This is from 12:30 to 2 p.m. in the Speakers Corner of Penfield Library. You can bring food and eat it there....
28 October
Practice: from chapter 7 do problems 1, 2, and 3a, 3b, 3c, 3d, 3e.
2 November
Practice: From chapter 8, do problems 1a, 1b, 1c, 1d, 2c, and 2d. Those from chapter 8 will require one or more indirect derivations. (Please note there is an error in the book; chapter 8, 2b is not a theorem! I'll fix that asap.)

More demands of you! You should watch these five videos by Dr. Chew, now that you've taken your test and had time to reflect on logic and your work. These will only take 30 minutes of your time and they are fantastic advice.
4 November
Read: chapter 9 of the book.
9 November
Practice: from chapter 9 do problem 1.
11 November
Read: chapter 11.
16 November
Read: chapter 12 of CIL.
14 November
Practice: do problems 1, 2, and 3 of chapter 11.
18 November
Quiz 2: all of the propositional logic (new things are indirect proofs and biconditionals), plus translating with names and predicates (but not with quantifiers yet).

Read: chapter 12 of CIL.
21 November
Read: chapter 13 of CIL.
28 November
Read: chapter 14 of CIL.

You should print, and keep with you, chapter 10 (a complete introduction to the propositional logic and chapter 16 (a complete introduction to the First Order Logic. These links are to pdfs of my own version of the book; they are not as nicely formatted but they are printable.
30 November
Practice: from chapter 12, do problem 2.
2 December
Practice: from chapter 13, do problem 1.
5 December
Practice: from chapter 13, do problems 2 and 3.

Problem 2c is the hardest we've done all semester! But, as a hint, look at the second example in section 9.6 of the book. The structure of part of that proof is similar to what you will need.

Extra: I promised some extra practice for translations using quantifiers. Here's something you can do this week for extra credit if you like.
Domain of discourse: people

Fx: x likes strawberry poptarts.
Gx: x is a barbarian.
Hx: x likes schmors poptarts.
Ix: x is civilized.
Jx: x is a gourmand.
a: Tony
b: Sam
  1. Some like strawberry poptarts.
  2. All who like strawberry poptarts are civilized.
  3. All who are not civilized do not like strawberry poptarts.
  4. Some don't like strawberry poptarts.
  5. Tony likes schmors poptarts but Sam does not.
  6. No one who likes strawberry poptarts likes schmors poptarts.
  7. Anyone who likes schmors poptarts is a barbarian.
  8. No one likes schmors poptarts.
  9. Some who like schmors poptarts are not gourmands.
  10. Some who like strawberry poptarts are gourmands.
  11. Sam is civilized if and only if Tony isn't.
  12. No one is a civilized barbarian.
6 December
Some extra office hours: I'll be available from 2-3 pm, and perhaps longer if required.
7 December
Practice: from chapter 14, do problem 1.

Some hints: variables are just placeholders! Don't get scared if a formula uses a different variable. Remember how in math you don't care if we use x or y. Also: the last three problems are hard! Look at my proof at the end of the chapter for some ideas. But most of all, if you can't do them, that's OK. Think of them as extra credit!