PHIL 347 Critical Reasoning
Week 3 Diagramming, Logical Strength, and Premise Evaluation
Directions: Type the letter answer into Canvas. You may also include the whole line. The letter
comes before the line or sentence
Example:
[A] Paris is the biggest city in France. [B] It is a major cultural center with many famous
museums. [C] The most famous of these museums is the Louvre.
In this passage, A = Paris is the biggest city in France. B = It is a major cultural center with many
famous museums. C = The most famous of these museums is the Louvre.
Section 1: Diagramming Arguments
Diagramming shows how claims relate to one another. An argument may contain different types
of claims:
• Some serve as reasons leading to a conclusion
• One or more may state conclusions
• Some may simply provide background information (these are called extra claims)
Premise claims can relate to the conclusion in three ways:
• They may converge independently on the conclusion
• They may link together and jointly support the conclusion
• They may form a chain, where one conclusion serves as a premise for the next
Claims that don’t support the conclusion in any of these ways are not part of the argument and
are excluded from diagrams. To diagram, number the claims in order of appearance, then build
from there. Refer to Chapter 7, pages 169–180, for more on diagramming.
Independent Convergent Claims
These claims each give a separate reason for the same conclusion. They indicate inductive
arguments.
Example:
(1) Cocaine is addictive, and (2) it is illegal, so (3) you shouldn’t use it.
Diagram:
1 2
\ /
3
Dependent or Linked Claims
These claims work together and must be combined to support the conclusion. This usually
signals a deductive argument.
Example:
(1) Cocaine is a drug, and (2) drugs are illegal, therefore (3) you shouldn’t use cocaine.
Diagram:
1 + 2
↓
3
Chained Claims
Here, the conclusion of one argument becomes a premise for another.
Example:
(1) If I study for my exam, I’ll do well.
(2) If I do well on the exam, I’ll pass the course.
Therefore, (3) if I study, I’ll pass the course.
Diagram:
1
↓
2
↓
3
Passage 1: Anyone who regularly practices meditation reduces their overall stress levels. Jordan
meditates every morning before work. Therefore, Jordan’s stress levels are lower than they
otherwise would be.
Question 1: Which is the correct way to diagram this argument?
a. Independent convergent claims
b. Dependent or linked claims
c. Chained claims
Passage 2: Either the power outage came from a blown transformer or from scheduled
maintenance. If it came from scheduled maintenance, the company would have sent a warning.
No warning was sent. So, the outage must have come from a blown transformer.
Question 2: Which is the correct way to diagram this argument?
a. Independent convergent claims
b. Dependent or linked claims
c. Chained claims
Passage 3: The museum is worth visiting. It has a rare collection of West African artifacts, its
architecture is stunning, and it only costs five dollars to enter.
Question 3: Which is the correct way to diagram this argument?
a. Independent convergent claims
b. Dependent or linked claims
c. Chained claims
Passage 4: You shouldn’t rely on Carl’s directions. He gets lost easily, and he hasn’t been to this
part of the city in years.
Question 4: Which is the correct way to diagram this argument?
a. Independent convergent claims
b. Dependent or linked claims
c. Chained claims
Passage 5: Vera repaired her bicycle’s chain last week. That means the bike should run more
smoothly. And if it runs more smoothly, she should be able to complete her commute faster. So,
Vera will probably get to work earlier than usual today.
Question 5: Which is the correct way to diagram this argument?
a. Independent convergent claims
b. Dependent or linked claims
c. Chained claims
Passage 6: A plant can thrive only if it receives enough sunlight. This one has been kept in a
windowless storage room, and its leaves are drooping badly. So, it definitely isn’t thriving.
Question 6: Which is the correct way to diagram this argument?
a. Independent convergent claims
b. Dependent or linked claims
c. Chained claims
Section 2: Logical Strength and Relevance
This section focuses on determining the strength of an argument. Refer to pages 197–292 to
prepare.
Passage 7: [A] All licensed drivers must pass a vision test. [B] Carla passed her vision test last
month. [C] Therefore, Carla is a licensed driver. [D] Licensed drivers are legally allowed to
operate a vehicle on public roads. [E] So, Carla is legally allowed to drive on public roads.
Question 7: Is this argument inductive or deductive?
a. Inductive
b. Deductive
Question 8: The argument addresses the issue.
a. True
b. False
Question 9: The premises support the conclusion.
a. True
b. False
Question 10: Each line is relevant to the conclusion.
a. True
b. False
Section 3: Evaluating Premises
Sometimes we accept claims without verification. Other times, we should dig deeper. Read pages
200–203 to learn when to accept a premise and when to check it.
Passage 11: Suppose a well-established economics journal reports, “Countries that invest
heavily in early childhood education tend to experience higher long-term productivity.”
Question 11: Would a critical thinker accept this claim, or check it out?
a. I’d accept that.
b. I’d check it out.
Passage 12: Suppose an anonymous post on a neighborhood forum claims, “The local grocery
store has been secretly selling meat contaminated with toxic chemicals.”
Question 12: Would a critical thinker accept this claim, or check it out?
a. I’d accept that.
b. I’d check it out.
Passage 13: Suppose an infomercial asserts, “This bracelet realigns your body’s energy field and
instantly improves memory and concentration.”
Question 13: Would a critical thinker accept this claim, or check it out?
a. I’d accept that.
b. I’d check it out.
Passage 14: Suppose a viral TikTok video says, “Eating three raw cloves of garlic before bed
guarantees perfect skin in two weeks.”
Question 14: Would a critical thinker accept this claim, or check it out?
a. I’d accept that.
b. I’d check it out.
Passage 15: Suppose a report from the U.S. Geological Survey states, “Seismic sensors show
that last year saw a slight increase in moderate earthquakes globally.”
Question 15: Would a critical thinker accept this claim, or check it out?
a. I’d accept that.
b. I’d check it out.