PHL111 Valid Reasoning, Past Assignments




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

31 August
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).
5 September
Reading: Read chapter 2 of the book.
7 September
Practice: Complete problems 5 and 6 at the end of chapter 2. (I've been asked about how to do this. For each problem (that, is for 5 and then for 6) make one translation key, showing what each atomic sentence letter means in English. Each atomic sentence in your key should correspond to an atomic sentence in English. So, look through the problems in 5 (a-j), identify all the atomic sentences, write them down, and tell me which letter corresponds to each sentence. Your key will look like:
KEY
P: Josie is a cat.
Q: Josie is a mammal.
R: Josie is a fish
...
Then, after having done that, and using your key, translate all those sentences. Do the same again for 6.)

Philosophy club meets at 4:30pm in MCC 211. The meeting will be a showing of the 2017 movie Annihilation.
12 September
Read chapter 3 of our textbook.
14 September
Homework listed below! Two quick points.

* A reminder: we have a no-phones, no computers policy in class. I know that's hard! We are all used to checking snapchat or scores or whatever every ten seconds. But psychologists have proven that no one is good at multi-tasking--you will inevitably miss out if you cruise the web during class, and the people around you will be distracted too. I don't grade for attendance, so you can skip class without penalty if you need to text or watch some video or whatever. My goal is to create a place and time where we all try to be focussed, that's all. Thanks!

* I defined "argument" in a very thin way: as an ordered list of sentences, one of which we call the conclusion, and the others which we call premises. Then, we distinguish good from bad arguments by saying the valid arguments are the good ones; all arguments that are not valid are bad. But sometimes in colloquial English people use "argument" to mean an argument that is valid or that at least has some other good feature. Here is a famous example (at 2:15)!

Homework: Since our last translations didn't go so well, let's try again.

Translate the following sentences from English into our logical language, the Propositional Logic. Provide one key for the entire assignment that shows to which (hopefully atomic) English sentences your propositional logic sentence letters correspond. Always try to show as much as you can about the structure of the sentence in our logic (that is, don't translate them all as a single letter, like P). Hand in your answers and translation key at the beginning of class. Write your homework neatly, since I might want to show yours on the overhead as an example.

For these problems: The last one is hard! It nests "if... then..."s. Try it. Also, think hard about "material" and "immaterial" -- can you show their relation using our logic (using one idea standing for "material")? It would be best if you could. Number 9 is tricky. Remember our discussion of "only if."
  1. The mind is brain activity.
  2. The mind is material.
  3. The mind is immaterial.
  4. If the mind is immaterial, then the mind is not brain activity.
  5. If mind is brain activity, then the mind is material.
  6. Provided the mind is not immaterial, then the mind is brain activity.
  7. Alzheimers is a disease of the mind.
  8. If the mind is brain activity, then Alzheimers is a disease of the brain.
  9. The mind is brain activity only if the mind is material.
  10. If the mind is brain activity, then Alzheimers is a disease of the mind only if Alzheimers is a disease of the brain.
What do we mean by "translation key"? We mean a translation from English to our logical language. Suppose instead one of our sentences was....
8. Spongebob pays no property taxes, if Spongebob lives in Bikini Bottom.
You identify the atomic sentences inside that complex sentence, and then make a key. There are two atomic sentences in this sentence, so your key would include the following:
English ..................................... Propositional Logic
Spongebob lives in Bikini Bottom........... P
Spongebob pays property taxes........... Q
Note that we took out the negation. We want to handle negations with our "¬" symbol. And then if you translated the sentence:
8. (P → ¬ Q)
Someone would be able to use your key to determine how to translate your logical sentence back into an equivalent English sentence.

So, for this homework, you'll write instead one key (put it at the top of the page), which will have a column of atomic English sentences, and beside it a column of atomic logic sentences (P, Q, R....). Then, and only then, write up the homework.