9 Law of Excluded Middle Examples

The “law of excluded middle” is a principle in logic that states that any proposition or statement must either be true or false. There is no third option or possibility.

This law may seem simple and obvious, but it has important implications for reasoning and decision-making. It allows us to make clear distinctions between what is possible and what isn’t, which helps us to evaluate arguments and draw logical conclusions.

For example, let’s say someone argues: “Either John will get the job, or Mary will get the job.” According to the law of excluded middle, this statement must be accurate – one will get the job (assuming there are no other candidates). We cannot say both will get the job, nor can we say neither will.

The Law of Excluded Middle has numerous applications across various fields. Let’s look at a few examples.

 9 Areas Where the Law of Excluded Middle is Applied

1. Artificial Intelligence

Scenario: Say you are creating an AI program that decides whether something is good or bad. The program would choose one option, with no room for anything in between.

Artificial Intelligence involves creating decision-making processes based on binary outcomes. Binary outcomes are simply two possible results, ones and zeros, like yes or no and true or false. The Law of Excluded Middle is used in AI programming to help make these decisions. It means there can only be one of the two possible outcomes – no middle ground.

2. Physics

Scenario: Imagine flipping a coin. It can land on heads or tails; it cannot be both simultaneously.

The Law of Excluded Middle is used in physics, specifically in quantum mechanics, to indicate that a particle can only have one specific state at any given moment; it cannot simultaneously be in two different states. This law helps physicists predict and calculate how particles will behave under certain conditions. By knowing that a particle can only exist in one state at a time, scientists can more accurately determine its behavior and properties.

3. Legal Proceedings

Scenario: Someone is arrested for possessing stolen property and charged with the crime. The court would rely on evidence to determine whether the accusation is true (the defendant stole it) or false (the defendant did not steal it).

In legal cases, the Law of Excluded Middle principle helps determine a verdict by relying on concrete evidence and proof to establish the truth of a claim or allegation. Either the defendant is guilty of participating in illegal activities or not.

4. Medical Diagnosis

Scenario: You go to your doctor with symptoms like coughing, fever, and sore throat. They suspect you have strep throat, but they won’t know for sure until they do some tests. The results will come back positive or negative for strep throat bacteria.

Medical diagnosis is like solving a puzzle; the doctor looks at all the clues and pieces them together to make a final decision. The law of excluded middle is an important part of this process because there are only two possible outcomes: either the person has the disease, or they don’t.

5. Contract Law

Scenario: Mary offers to sell her car to Jane for $10,000. Jane accepted the offer, and they signed a contract. However, Mary later discovers that she made a mistake in her calculations, and the car’s actual market value is $15,000. She wants to back out of the contract.

In contract law, the Law of Excluded Middle is used to determine whether a contract is valid or not. For a contract to be valid, there must be a clear offer and acceptance, a legal object, and consideration. If any of these elements are missing, the contract is invalid. The contract is valid in this case since there was a clear offer and acceptance, a legal object, and consideration. Mary cannot back out of the contract simply because she made a calculation mistake.

6. Psychology

Scenario: A study shows that people who exercise regularly have lower anxiety levels than those who don’t. This finding can either be true or false.

The Law of Excluded Middle establishes cause-and-effect relationships between variables in psychology research studies. That means that they try to show whether one thing is directly causing another thing to happen. In our scenario, they would use the Law of Excluded Middle to determine whether exercising causes lower anxiety levels or if some other factor is involved. By using this principle, psychologists can more accurately understand how different variables relate and make better predictions about human behavior.

7. Ethics

Scenario: In a debate, you and another party discuss whether it’s okay to steal. You would have to decide whether stealing is always wrong or if it can be justified. You can’t argue, “Well, maybe stealing is kind of wrong but also kind of right,” because something can’t be both at the same time.

When applying the concept of the Law of Excluded Middle to ethics, we have to make a clear decision about what’s right and what’s wrong based on our own beliefs and values. It may not always be straightforward, but it ensures our actions are consistent with our moral principles.

8. Logic

Scenario: You’re trying to decide whether to bring an umbrella with you today. If someone tells you, “It’s raining outside,” according to the law of excluded middle, this statement must be either entirely true or false.

In our scenario, if we say, “It’s raining,” then the opposite of this statement (“It’s not raining”) must also be true because there are only two possibilities – it’s either raining or not. The law of excluded middle serves as a guideline for ensuring logical reasoning and clarity in our thinking processes. It ensures that we are transparent when making decisions based on specific facts.

9. Science

Scenario: Let’s say we want to test the effectiveness of a new drug in treating a specific disease. We can set up a study in which half of the participants receive the drug, and the other half receive a placebo. We then measure the outcomes and compare the results of the two groups.

In this situation, the outcome of each participant is designed to only fall into two categories – either they were cured or not. There can be no third possibility. This makes it easier for scientists to compare the drug’s effectiveness versus the placebo since they only need to look at the two possible outcomes.


The Law of Excluded Middle is an essential and fundamental principle in logic that has applications in various scenarios. The significance of this principle lies in its ability to establish clear boundaries and parameters within logical arguments and reasoning. It serves as a basis for many other logical principles and concepts crucial to various fields of study.