Arguments and Philosophical Reasoning

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Area: Math and Logic
Grade Level: High School & Beyond, Middle School
Topics: Arguments and philosophical reasoning, logic, math, monty python, premise, reason
Estimated Time Necessary: 50 minutes

Lesson Plan

Introduce students to philosophical arguments
Explore the types of logical reasoning used to investigate philosophical issues

Materials needed

  • Chalkboard or whiteboard
  • Computer and projector or equipment to watch short video clips from the web

This lesson can be used at any time in a philosophy course, for a meeting of a philosophy club or discussion group, or for a workshop. Because it introduces students or participants to the method of how philosophers approach philosophical questions, it is especially appropriate as a first lesson or experience. It is intended to get students or participants to recognize that philosophical reasoning takes place in the form of argumentation. This lesson, however, stops short of providing tools for evaluating philosophical arguments. Therefore, if you are using this as the first lesson in a class or for a first meeting of a philosophy club or interest group, it would be natural to follow it up with some lessons on critical thinking or logic to provide a more complete foundation in philosophical reasoning. In turn, those lessons could be followed by explorations of philosophical content, in which you would use the method of philosophical reasoning to address specific philosophical questions or topics.


Am I Your Teacher? (10 minutes)

  1. Begin by writing “I am the teacher of this class” (or whatever would be most appropriate for your setting) at the bottom of the board with a line drawn above it. Ask the students or participants to show by raising hands how many of them think this statement is true. Presumably, all of them will. If so, ask them why they think this. As they give reasons, write the reasons on the board above the line. Once there are a large number of reasons on the board, ask them what everything written on the board together is called. The purpose is to illustrate that an argument is being made.

I told you that I am the teacher.

I am standing at the front of the class.

I am leading this exercise.

I am the only adult in the room.


I am the teacher of this class

  1. Ask the students or participants why they think you had them do this as the first exercise when exploring philosophy. Lead a brief discussion. A few points to try to develop during the discussion include:
  • What you have written on the board is an example of an argument
  • Arguments are the way we think and reason—when we’re reasoning something out, what we’re doing is forming a series of arguments in our heads
  • Philosophy is essentially a process of thinking systematically about difficult and interesting questions, and a primary component of philosophy centers on making and evaluating arguments.

 What Is an Argument? (10 minutes)

  1. Begin this activity by showing the Monty Python clip, “The Argument Clinic.”
  2. After showing the clip, ask:

What are the two different concepts of “argument” presented in the skit?

The two concepts are:

  • Mere contradiction or a dispute (Yes it is… No it isn’t… Yes it is… No it isn’t…)
  • (Proposed by the customer) “A collected series of statements to establish a definite proposition.”

When we talk about arguments as used by philosophers, we are talking about an argument in the latter sense. Again, doing philosophy is essentially a process of making and evaluating arguments.

Parts of an Argument (10 minutes)

  1. Return to the “I am the teacher of this class” argument. You’ll use it as an example to illustrate and help explore what arguments are and how they work.
  2. In a group discussion, explore the parts of an argument. As you do so, it will be helpful to develop the following points and to introduce the following terms:

Ask what parts constitute an argument. What are its basic building blocks? Arguments are composed of sentences. In fact, they are made up of a particular type of sentence, known as a proposition.

Proposition: A declarative sentence that has a truth value. In other words, a proposition is a sentence that can be either true or false. To be precise, propositions express facts about the world that can either be true or false. Examples include “Today is Monday” and “It’s raining outside.”

Question: Are there kinds of sentences that are not propositions? Answer: Yes. Questions, commands, exclamations, etc., are all types of sentences that are not propositions because they lack a truth value. Examples include “Go open the door,” and “What is today’s date?”

Typically, most of the propositions in an argument state facts or provide information which support the claim being made. These propositions are known as premises.

Premise: A proposition serving as a reason for a conclusion.

The claim being made is known as the conclusion of the argument.

Conclusion: A proposition that is supported or entailed by a set of premises.

Arguments always have one conclusion, but the number of premises can vary quite a bit. The “I am the teacher of this class” argument has several premises.

Question: Can there be an argument with only one premise? Answer: Yes. For example, “Bill is an unmarried male. Therefore, Bill is a bachelor.”

Question: Can there be an argument with no premises? Answer: Yes. For example, consider an argument with no premises and the following conclusion: “It is either Monday in Tokyo or it is not Monday in Tokyo.”

It’s worth noting that adding premises doesn’t necessarily add support for a conclusion. For example, the argument above with no premises is in fact a compelling argument, since it always has to either be Monday or not be Monday in Tokyo.

  1. Now we can say what an argument is in a more precise way:

Argument: An argument is a set (a collection) of propositions in which one proposition, known as the conclusion, is claimed to derive support from the other propositions, known as premises.

  1. To summarize:
  • Arguments are the way we think and reason—when we’ve reasoning something out, what we are really doing is forming a series of arguments in our heads.
  • Though “argument” can also mean a dispute in common use, that’s not the sense in which we mean it when doing philosophy.
  • Arguments consist of a conclusion and (almost always) some premises.
  • The conclusion is what the argument is meant to support as being true; it’s the claim being made.
  • The premises provide support for the conclusion.
  • There can be any number of premises, from 0 to an infinite number (but having more premises doesn’t necessarily mean there is more support for the conclusion!).
  • The premises and conclusion are propositional statements; that is, they are sentences that express facts (propositions) about the world that may be true or false.

Argument Dissection (10 minutes)

The “I am the teacher of this class” argument is in normal form. That’s just a fancy way of saying that the premises have been collected together in a list with the conclusion following them. Often, we separate the conclusion from the premises by drawing a line between them (or by putting in the symbol \, which means “therefore,” before the conclusion) to make it very clear which proposition is the conclusion. Usually arguments written in English prose are not so simply presented. The conclusion may be stated first, or for stylistic reasons it might not be at either the beginning or the end of the prose. Converting an argument from English prose into normal form allows us to clearly pick out the premises and conclusion.

How can we identify the premises and the conclusion of an argument in ordinary prose? It can take some judgment, but we are usually guided by indicator words. The propositions in arguments are often accompanied by words that indicate whether that proposition is a premise or a conclusion.

As a group, brainstorm words or phrases that might indicate that the proposition they introduce is a premise or a conclusion. The following lists provide some of the most common premise and conclusion indicators.

Premise Indicators: since, because, for, in that, as, given that, for the reason that, may be inferred from, owing to, inasmuch as

Conclusion Indicators: therefore, consequently, thus, hence, it follows that, for this reason, we may infer, we may conclude, entails that, implies that

With that background in hand, the next activity will help everyone see that arguments are in fact all around us and help them to identify more easily the structure of those arguments, which is an important first step in evaluating whether we should be convinced by the argument.

  1. Hand out to each student or participant a couple of arguments you have found in editorials, blogs, philosophy texts, or wherever. Ask them to re-write the arguments in normal form, identifying the premises and the conclusions.
  2. When done, ask everyone to pair up. Each person should show his or her partner the original arguments and the rewritten arguments in normal form. Each pair should then discuss whether or not the premises and conclusions were correctly identified. Float throughout the room and answer questions.

Evaluating Arguments (10 minutes)

This is a fun activity to help everyone start thinking about how to evaluate whether we should be convinced by an argument. Begin this activity by showing the Monty Python clip, “She’s a Witch!

Begin a discussion about whether people are convinced by the argument provided in the video clip. Try to focus the discussion on whether the premises provide good reasons for believing that the conclusion is correct. Note that until the characters in the video clip actually use the scale, they don’t know whether some of the facts asserted in the premises are true. That’s often the case in exploring philosophical questions. What’s important is the logical relationship between the premises and the conclusion. Hypothetically, if the premises were all to turn out to be true, would they then make it likely that the conclusion would also be true? By asking that question, we can evaluate the reasoning in an argument. Philosophers often focus the most on this step. If the reasoning in an argument is good, then we can go on to ask whether the premises are in fact true. Often that requires empirical investigation (and so may require the aid of scientists or other specialists). If both are the case—the reasoning is good and the premises are true—only then should we assent to the conclusion.

After a few minutes, pause the discussion. Ask the students to write a paragraph defending why they are or are not convinced by the argument in the video clip. Remind everyone that the paragraph should, of course, take the form of an argument!

If this lesson is being used for a one-time event, you can ask some volunteers to read their paragraphs and then resume a discussion about what they learned. If you are using this lesson as part of a class or a series of meetings, you can always ask the students or participants to write the paragraph at home and bring it with them to the next meeting. You can then discuss their paragraphs and what they learned from the exercise. If you are teaching a formal course, you can have the students turn in their paragraphs as an assignment.

Follow-Up and Conclusions

If this lesson is part of a course or a long sequence of meetings, it would be worthwhile to follow up with another lesson or two on how to properly evaluate arguments. How that is done will depend on how formal or informal you want to be in thinking about logic, and also how long you want to spend on an introductory philosophical reasoning unit.

Supplemental Materials

There are a number of excellent textbooks and resources on arguments, critical thinking, and logic. For example, reading the first two chapters of the following logic textbook would prepare you thoroughly for leading this lesson:

Hurley, Patrick. A Concise Introduction to Logic (Twelfth ed.). Stamford: Cengage Learning, 2015.

(As an aside, reading the third and fourth chapters of the Hurley text would prepare you well for a potential follow-up lesson on distinguishing deductive from non-deductive arguments and evaluating arguments.)

A supplementary text with a more informal discussion of arguments is the following:

Weston, Anthony. A Rulebook for Arguments (4th ed.). Indianapolis: Hackett Publications, 2009.

The following brief magazine article was written by the authors of this lesson and, in a fun way, explores how philosophers investigate philosophical questions:

Gluck, S. and Rodriguez, C. “The Philosopher’s Toolbox,” Imagine 17.4 (2010): 20-21.

(Available online here)

This lesson plan, created by Stuart Gluck and Carlos Rodriguez, is part of a series of lesson plans in Philosophy in Education: Questioning and Dialogue in Schools, by Jana Mohr Lone and Michael D. Burroughs (Rowman & Littlefield, 2016).

This lesson plan was created for PLATO by: This lesson plan, created by Stuart Gluck and Carlos Rodriguez, is part of a series of lesson plans in Philosophy in Education: Questioning and Dialogue in Schools, by Jana Mohr Lone and Michael D. Burroughs (Rowman & Littlefield, 2016)..

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