By Stephanie Gibbons and Justine Kingsbury, adapted by Marc Chao and Muhamad Alif Bin Ibrahim

Learning to form arguments is a fundamental aspect of developing critical thinking skills, which are essential in psychology and many other fields. While it might seem like an exercise more suited to an English class, the ability to construct and analyse arguments is crucial for evaluating evidence, making informed decisions, and understanding complex issues. In psychology, forming arguments helps us to systematically assess theories, interpret research findings, and engage in scientific debates. This process involves not just presenting information but also providing logical reasoning and evidence to support our conclusions.

This is not an “English” class because our focus is not on language arts or literary analysis. Instead, we are concerned with the principles of logical reasoning and the application of these principles to psychological concepts. By learning to form well-structured arguments, we enhance our ability to think critically about psychological phenomena, identify cognitive biases, and improve our research methodologies. This skill set is invaluable for conducting rigorous scientific research and for applying psychological knowledge in practical, real-world situations.

In this book, we use the term “argument” in a more technical sense. In everyday language, any kind of verbal disagreement is often called an argument. For example, consider a discussion between two colleagues about the effectiveness of a new workplace policy. One colleague insists that the policy has significantly improved productivity, while the other disagrees. Their conversation might go like this:

This exchange, although a verbal disagreement, does not constitute an argument in the sense we will be using the term. They were making contradictory statements without providing any supporting reasons.

An argument, as we will define it, is a set of statements that includes a conclusion and reasons to support that conclusion. If either colleague had provided reasons for their claims, they would have had the beginnings of an argument. For instance, one colleague might believe the policy is effective because they have observed a decrease in project completion times. The other might disagree because they have noticed an increase in employee stress levels.

Notice that they are no longer just contradicting each other (“Yes, it has!” “No, it hasn’t!”). Instead, they are providing reasons to support their assertions, thus forming arguments.

Not all statements or writings constitute an argument. A piece of speech or writing qualifies as an argument only if the speaker or writer aims to persuade someone of a particular point by offering reasons to support its validity.

Propositions and Arguments

Premise

The term “premise” refers to a reason or basis for believing or concluding something. Premises are statements that form the foundation of an argument. For example, if I observe that I am getting wet while standing outside, this can serve as a premise to support the conclusion that it is raining. In this case, both statements, “I am getting wet” and “It is raining”, are propositions about the state of the world, but they serve different roles. The first statement, “I am getting wet”, provides a reason to believe the second statement, “It is raining”. Therefore, the first proposition is a premise, and the second is a conclusion.

It is important to note that not all propositions are premises. For a proposition to be a premise, it must support another proposition, which is the conclusion. Only when a proposition is used in this supportive role does it become a premise.
Suppose someone says, “The roads are slippery because it rained last night”.

• In this statement, the proposition “It rained last night” functions as a premise, because it provides the reason for believing the conclusion that “The roads are slippery”.
• On the other hand, if the proposition “It rained last night” is simply mentioned in isolation as a piece of information, such as in the statement “It rained last night, and I enjoyed listening to the sound of the rain”, it is not a premise because it is not being used to support any conclusion.

Thus, whether a proposition is a premise depends on its role within the context of an argument. Only when it supports a conclusion does it become a premise.

Proposition

A “proposition” or “declarative statement” is a sentence that makes a claim about something that can be either true or false. The terms “declarative statement”, “proposition”, and “statement” are often used interchangeably.

Critical thinking involves figuring out what to believe, what we know, what is true and reasonable, and what is worthwhile. Propositions are the statements that express or summarise our beliefs and knowledge, unlike other statements that ask questions or give directions. This book will focus on propositions and not cover other types of statements. Make sure you understand what a proposition is and why it is important to critical thinking before moving on.

Language is the tool we use to accomplish almost everything in our lives. The parts of our language that express our thoughts, beliefs, and knowledge are called propositions. To become skilled critical thinkers, it is essential to understand these types of statements, their functions, how to evaluate them critically, and how they are used in reasoning (i.e., arguments).

The key feature of a proposition, unlike other types of statements, is that it can be “true” or “false”. Questions and commands are not the types of statements that can be true or false; they serve different purposes.

As discussed in the “Premise” section above, propositions can serve various roles, such as premises or conclusions in arguments. For example, the statement “I am getting wet” is a proposition because it makes a claim that can be true or false. If this claim is true, the proposition can serve as a premise to build an argument that supports another proposition, called a “conclusion”, such as “It is raining”. In this way, conclusions, like premises, are also propositions whose truth depends on the truth of the premises provided. Organising sentences with premises and a conclusion is known as an “argument”.

Argument

An argument is a group of propositions or statements that form a piece of reasoning. Reasoning involves using certain information (called premises) to derive other information (called conclusions) through inference. An inference is the mental process of connecting premises to reach a conclusion that logically follows from them.

In an argument, one or more propositions serve as premises or reasons, and one proposition serves as the conclusion. An argument must have at least two propositions or statements, but it often includes more. For example:

Here, the premises are logically connected and lead to the conclusion.

A single statement cannot be a complete argument. For example:

This is not an argument because it presents only a conclusion without any premises to support it.

Statements within an argument must be related in a way that establishes a reason-and-conclusion relationship. If the propositions do not relate to each other in this way, they do not form an argument. For example:

These statements do not relate to each other in a way that establishes a reason-and-conclusion relationship, so they do not form an argument.

The purpose of an argument is to convince others of the conclusion. Just as one should not hold a belief without a reason, one cannot have a conclusion without premises. The sentences in an argument are all propositions or declarative statements, each serving different roles within the argument structure. The role of the premises is to support or justify the conclusion. While an argument can have only one conclusion, it can have multiple premises. In an argument, premises are assumed to be true, though this does not guarantee their truth; they are not justified within the argument itself. Other arguments likely justify these premises, where they would serve as conclusions.

The effectiveness of premises in supporting the conclusion and the credibility of their connection to the conclusion are critical aspects of analysing arguments.