Arguments are the fundamental components of all rational discourse: nearly everything we read and write, like scientific reports, newspaper columns, and personal letters, as well as most of our verbal conversations, contain arguments. Picking the arguments out from the rest of our often convoluted discourse can be difficult. Once we have identified an argument, we still need to determine whether or not it is sound. Luckily, arguments obey a set of formal rules that we can use to determine whether they are good or bad.
In this unit, you will learn how to identify arguments, what makes an argument sound as opposed to unsound or merely valid, the difference between deductive and inductive reasoning, and how to map arguments to reveal their structure.
Completing this unit should take you approximately 7 hours.
Read this section, which differentiates an argument in the logical sense from the ordinary language sense of a heated disagreement and introduces you to the basic structures of logical argument: statements, premises, and conclusions.
Complete Exercise 1, identifying which sentences are statements. Once you identify them, begin thinking about what premises might lead to those statements. When you finish, check your responses with the answer key.
If you would like to download the full textbook, it can be found here: Introduction to Logic and Critical Thinking.
Read this tutorial, which explains how to identify an argument by picking out its components. Complete the exercises and check your answers.
Read this section, which will give you some tips on how to spot an argument. While the premise and conclusion indicators are not guarantees of an argument, they can assist you in identifying an argument.
Complete Exercise 2, distinguishing arguments from non-arguments and identifying the conclusion of argument sentences. Despite the name, the conclusion often precedes the premises when we present arguments in ordinary language. When you finish the exercise, check your answers against the answer key.
Read this tutorial, which explains how to put an argument in standard form. Be sure to complete the exercise.
These sections will introduce you to the concept of validity – the term for when the conclusion of an argument follows from its premises. Pay careful attention to the difference between validity and soundness. All sound arguments are valid, but not all valid arguments are sound. Remember that premises do not have to be true for an argument to be valid.
Complete Exercise 5, checking your answers against the key.
Validity and soundness are two of the most important concepts in the study of arguments, and they are often confused with one another. Read these three tutorials on the distinction between valid and sound arguments, their relationship to the truth of the statements that make them up, and the structural patterns that help us to recognize them.
Complete the exercises and check your answers.
Complete this knowledge check, which tests your knowledge of the distinction between valid and sound arguments. Note that deductive arguments might be, but need not be, valid or sound; deductive arguments may be valid or invalid and sound or unsound.
Read these sections to learn how to round out arguments conceptually. The first section will distinguish between two types of argument: deductive and inductive. Pay careful attention to the difference between these two, and think about which kind of argument you use more often. The second section will help you identify arguments with a missing premise and determine how and when to supply this missing premise. It will also introduce you to the principle of charity and the difference between normative and descriptive statements – three very important terms! The third section shows you three rhetorical devices to hint at further argument without actually going through the argument: assuring, guarding, and discounting.
Complete the exercises, then check your answers against the keys.
When arguments are stated verbally or in writing, their structure may not be completely explicit. The section on hidden assumptions provides clues about how to identify hidden assumptions. The section on inductive reasoning introduces the important concept of induction. Inductive arguments form a whole second class of arguments, alongside deductive ones, and will be important in our unit on scientific reasoning later on. The final section puts together a number of the ideas laid out so far to describe the characteristics of a good argument.
Complete the exercises and check your answer.
Visualizing argument structure can help determine how directly or indirectly supporting evidence leads to a conclusion. This section gives examples of simple and more complex arguments using arrows to represent the structure of an argument. Complete the exercises and then check your answers. The answer key has the arguments in standard form, but there is no key for the diagramming.
Read this tutorial about how to construct an argument map. Argument maps are a way of visually representing the logical structure of an argument.
Read this section about an inductive argument many people use quite frequently: arguments from analogy. As you read, think about the difference between relevant and irrelevant similarities when it comes to analogies, as well as relevant disanalogies. Being able to identify these will help you make stronger inductive arguments.
Complete the exercise and check your work against the answer key.
Read this tutorial on analogical arguments. Arguments that are based on analogies have certain inherent weaknesses. This tutorial will help you find out how analogical arguments are structured and the most common ways they may be undermined.
Read this tutorial on reducing valid arguments to their basic structure using argument patterns. This text previews the kind of analysis we will do much more of in Unit 4. This kind of strategy is sometimes useful in analyzing arguments in real-life situations. For example, you might see these types of questions and find identifying argument patterns useful for the Law School Admission Test (LSAT).
Try to formulate examples of three important patterns of argument: modus ponens, modus tollens, and reductio. Then, for this argument sent to a newspaper by a reader responding to an article claiming that Shakespeare was Italian, identify the argument's main conclusion and spell out the argument's premises.
"So Shakespeare was an Italian, because almost half of his plays are set in Italy. Almost all of Isaac Asimov's novels are set in outer space – does that mean he was a Martian?" – Graham Simpson
Share your thoughts on the discussion forum. Make sure to review and respond to other students' posts, as well.