# PHIL110 Critical Thinking – SPS CUNY

PHIL110 Critical Thinking – SPS CUNY
Unit 10 Discussion Assignment
Take a Break!
This assignment first asks you to ‘Take a Break with Elmo and Big Bird’
Now that we’ve established our context, let’s have some fun with Elmo, Big Bird and Deductive
Propositional Logic. Let’s remind ourselves of a couple rules of deductive logic:
• An argument is deductively valid if and only if the truth of its premises guarantees the
truth of its conclusion.
• Or alternatively stated: An argument is deductively valid if and only if there is no way for
its premises to all be true and its conclusion to be simultaneously false.
• The following table represents some of most used symbols, feel free to copy and paste
them:

Let’s now consider the following set of propositions:
• Elmo is red.
• Big Bird is green.
• Either Elmo is red or Big Bird is green.
• Big Bird is green and Elmo is red.
• It is not the case that Big Bird is green
Once we know the truth-value of the first two sentences (whether they are true or false), we can
figure out the truth-values of the others.
For this assignment, complete the worksheet below and add it to the Discussion Forum. Then
read and comment on at least three students’ post by reviewing the completeness of their Truth
Tables.
Worksheet
(complete, then copy and paste the entire worksheet or the truth tables into the Discussion
Step 1. Represent these statements with variables and symbols. (For example E could stand for
“Elmo is red,” and B for “Big Bird is green,” but feel free to change these variables per your own
preference). Complete this table below:
PHIL110 Critical Thinking – SPS CUNY

Step 2. Complete the following simple table with four combinations of T and F, when T (stands
for true) and F (for false):

Step 3. Now complete the Truth Table for the rest of the sentences (T stands for true, and F
stands for false). The color-coding will help you determine where some of the same information
can be transferred over from the previous tables.

PHIL110 Critical Thinking – SPS CUNY
Step 4.
Interpret what this Truth table tells you. What’s your claim regarding Elmo and Big Bird’s
colors using the truth table you constructed? Does the information (T and F) from your Truth
Table align with reality? How is this process and constructing a Truth Table useful?
End of the Worksheet