2. What are two ways of reasoning?

What is an argument?

An argument is used to prove or support a statement. An argument always has two parts: a premise and a conclusion. If a statement does not consist of these two parts, it is not an argument. "God exists" is not an argument, and "God exists, and if you don't believe that then you will go to hell," neither. The latter is just a way to scare you, not an argument.

 "Something has had to create the universe, so God exists" is an argument. The premise supports the conclusion that is being drawn. A premise is aimed at providing reasons for accepting that conclusion.

How do the conclusion and the premise relate to each other?

The same statement can be the conclusion of one argument and the premise of another argument. An example:

  1. Premise: The brakes, engine and steering wheel of the car are broken.
  2. Conclusion 1: The car is no longer usable.
  3. Conclusion 2: We need to buy a new car.

The statement "The car is no longer usable" is the conclusion that follows premise 1, but it also forms the premise for the conclusion that a new car must be purchased. Claim 1 is therefore, in addition to a conclusion, also a premise for Claim 2.

What do we mean by unspoken premises?

It often happens that arguments contain unspoken premises or conclusions. An example of an unspoken premise:

1. You cannot borrow books without a library card.

2. Jan cannot borrow books from the library.

The unspoken premise here is that Jan does not have a library card. This explains the reason he cannot borrow books from the library.

In addition, conclusions can also be unspoken. An example: "The political party that is most seen as the voice of the people will win the elections. The labour party will therefore win the elections. " The unspoken conclusion here is that the labour party is seen as the voice of most people.

What are two types of arguments?

Good arguments can be both deductive and inductive.

Deductive arguments

Words like "because", "since" or "this is explained by", are often followed by a premise. In cases like these, the premise thus comes after the conclusion. For example, you can claim that you are sad because your partner has forgotten your birthday.

  • The premise in a good deductive argument proves the conclusion that is drawn from a logical point of view.
  • For deductive reasoning, validity is very important. An argument is called valid when it is not possible that the premise is true, and the conclusion is false.

An example:

Premise: "John was chairman before Marc and James was chairman after Marc.

Conclusion: "John was chairman before James was chairman".

It is impossible in this example that the premise is correct, and that the conclusion drawn is not. The premise of a good deductive argument, therefore proves the conclusion. There is therefore a valid argument. If the premise of a valid argument is true, the argument is justified. This is what we call a sound argument.

Inductive arguments

The premise of an inductive argument does not prove the conclusion - but it does support the conclusion. An inductive argument does not have the same true or false kind of deal as a deductive argument does. Support for a conclusion is provided in varying levels with an inductive argument. An example is that the perpetrator of a murder is sought. A woman has been killed and her husband is known to have repeatedly threatened her. This is certainly not proof that he killed her and does not support the claim that he killed her. But let’s say his fingerprints were found on the murder weapon. This is still not proof of the claim that he actually committed the crime, but this fact gives more support for the claim that he killed her.

A good inductive claim therefore indicates that the conclusion that follows is the one that is most likely to be true. With inductive arguments:

  • The more a premise supports the conclusion of an inductive argument, the stronger the argument is.
  • The less a premise supports the conclusion of an inductive argument, the weaker the argument is.

To find out if an argument is deductive or inductive, it is important to read well. The difference between a deductive and inductive argument is that with induction there is a ‘most likely’ possibility, and with deduction there is no other way than the conclusion to be true or false.

Beyond reasonable doubt

Inductive arguments are often used in the judicial process, for example to convict suspects. A person is found guilty if the claim is highly supported ("beyond reasonable doubt") that he or she has committed a crime. This evidence is less strong than deductive evidence. This is because with deductive arguments it is not the case that support comes in gradations. There is an all-or-nothing principle: a conclusion must be true if the premises are correct.

Deduction, induction and unspoken premises

It is not difficult to turn an inductive argument into a deductive argument. To achieve this, an universal premise must be added. This is a premise that serves as a rule on which no exception is possible.

Suppose someone says: "John and Mary are about to divorce. They constantly argue.” A deductive argument can be made of this statement when a universal rule is added, namely that all couples who are constantly arguing are about to divorce. It sometimes happens that a conclusion is based on a pronounced and an unspoken premise. An example: Imagine hearing two professors talking and one saying "Give him a failing grade, this is the second time you've caught him cheating!"

• Premise: "This is the second time he was caught when he was cheating".

• Unspoken premise: "Anyone who gets caught twice cheating during an exam must receive a fail for the exam."

• Conclusion: "He must get a fail".

In daily life, people often use unspoken premises. Due to the context and the content of the subject, we notice an unspoken premise regardless.

How can you weigh things in daily life?

Reasoning in daily life often has to do with weighing up beliefs against each other. This process is also called balance of beliefs (aka "balance of considerations reasoning"). It contains both deductive and inductive elements. If you make a trade-off, you look at how strong or weak an argument is with regard to induction, and how valid and correct the argument is with deduction.

Another way to reason is abduction ("inference to the best explanation"). Here, the most suitable explanation is looked at - the conclusion that correctly addresses all parts of the phenomenon. An abduction is an inductive argument. The appropriate declaration must meet the following characteristics:

  1. It explains the phenomenon most accurately
  2. It leads to the most accurate predictions.
  3. It is not contrary to other possible statements.
  4. It has the least unnecessary assumptions.

An example of this is: When I came home, I saw that my wife and dog were not at home. Her coat was not on the rack and the dog leash was gone too. Thus, the best explanation is that my wife is walking the dog.

The explanation meets all the conditions given in the situation and is therefore a valid argument.

When is something not an argument?

Argument identification is the recognition of arguments. Like stated a couple of times before, an argument consists of two elements: (1) a premise (or several premises) that supports (2) the conclusion. That way arguments can be recognized. There are words or phrases that are often used to show that a conclusion will follow. Examples are: "therefore," "so," "the conclusion is," and "this shows that." There are also words that are used to show that a premise will follow. Examples are: "given that" and “because”

But which things are not arguments? Pictures and videos are not arguments. They can be beautiful, they can be emotionally moving or they can be evidence, but not arguments. They can make you feel or think something, but they are not true or false - that is, with regard to claims and arguments.

"If ... then" sentences are also not arguments. They can form a premise or conclusion, but that is not yet an argument because it is not both. A list of facts is also not an argument because it offers no reasoning, and "A, because B" is also not because it’s more of a statement rather than an argument.

Logos, ethos and pathos

There are three levels of persuasion ("modes of persuasion"). Sometimes external factors can influence judgments. For example, if your mother thinks bad of something, it weighs more heavily in with your own judgment than the judgment of a stranger. Another example is someone who has a heavy British accent. The voice of such a person soon sounds noble and this can influence the judgment that is made about that person. This is called ethos.

Sometimes rhetoric is used to include external factors in, for instance commercials, in the decision to buy a product. It's about using powerful, psychological language that actually adds nothing. An example is that a commercial says that a product is "extra tasty" or "extra fresh." This is called logos.

In addition to the use of rhetoric, the use of photos or images can have a powerful influence on the emotions of viewers. In this way their judgments can be influenced by playing in on people’s emotions, sympathy and empathy. This is called pathos.

How can arguments be understood?

Many arguments are difficult to understand because they are not on paper and because they quickly pass by in a conversation. Premises and conclusions are therefore not easy to distinguish. When it comes to understanding an argument, it is important to first establish the conclusion. The next step is to find the premise (or premises) on which the conclusion is based. Next, the examples on which the premise(s) is or are based must be looked at, in case that examples are indeed given. These steps can be used to understand spoken arguments and written arguments.

When the relationship between premises and conclusions is understood, the structure of an argument is understood. When determining the premises, it is important to pay attention to words such as "because", "therefore" and "since". When arguments in a written story have to be analysed, it is smart to break the story into premises and to link numbers to these premises. The numbers can then be processed in a diagram that also makes use of arrows, so that causes (premises) and consequences (conclusions) can be better distinguished.

How can arguments be distinguished?

It is important to distinguish between what is an argument and what is a description, explanation or summary. This is not always easy. The question is whether someone uses reasons to support or prove his or her conclusion. If so, there must be at least some arguments in the story he or she tells. When an argument is evaluated, two things must be considered:

  • Logic: can the argument really be used to prove and/or support a conclusion?
  • Truth: are the premises correct at all?

Not everything is an argument. An argument always consists of two parts. Phrases that contain "if" and "then" are not arguments, because they list consequences, not conclusions. A list of facts is also not an argument. Phrases that contain "because" depend on what follows after it, you will have to decide for yourself whether they are an argument or not. If what follows provides proof, then it is an argument. If it indicates a cause, then it is not.

Example: "Jack is wearing swimming trunks because he was swimming" is not an argument. Here it explains the cause, the reason why he is wearing them.

"Jack was swimming because he was wearing his swimsuit" is an argument because it provides a reason. It is therefore important to read well and to understand what the sentence says.


Practice questions

  1. What is a deductive argument? What exactly is the relationship between the conclusion and premises? When can the conclusion be incorrect?
  2. What is the difference between a deductive and an inductive argument?
  3. Consider the following reasoning: "Up to now, induction has always worked well, so it is a method that will always work well."
    1. What kind of reasoning is this?
    2. Is it a convincing argument? Why (not)?
  4. What is the problem with induction? What could it mean for the justification of scientific knowledge?
  5. Out of which two parts is an argument usually built up?
  6. What is the difference between a deductive argument and an inductive argument?
  7. When is an argument valid?
  8. What three levels of persuasion exist?


  1.       A deductive argument consists of premises and conclusions. Premises are true statements, assumptions, and a conclusion that follows logically. If the premises are correct, the conclusion is that when you agree with the premises, you agree with the conclusion. For example:

P1 = horses are larger than humans and P2 = people are larger than ants, it follows that C = horses are larger than ants. The conclusion of a deductive argument can be incorrect in two cases. If one or more of the premises is incorrect (ants are larger than horses) and if the argument is invalid, that is, it is constructed in the wrong way - P1 = horses are larger than humans and P2 = ants are smaller than horses, you cannot conclude that people are larger than ants or that ants are larger than people.

  1.      The conclusion from a deductive argument is always true if the premises and the argumentation structure are correct. This provides certainty. However, this is a limited form of certainty; because what are we sure about? Where do we get the certain premises? And how do we ever come to new knowledge deductively reasoning? That the conclusion is certain is because it was already included in the premises. Strictly speaking, reduction does not provide any new knowledge.

New knowledge is possible with inductive reasoning. Inductive arguments are 'non-conclusive', or 'non-demonstrative', which means that the conclusion does not logically follow from the premises but is only supported by them. A conclusion from an inductive argument is therefore never certain. This is a disadvantage, but at the same time makes new knowledge possible. From the fact that all the ravens you've seen so far were black, you can conclude that all ravens are probably black.

  1.      This is an inductive reasoning because a conclusion (it will always work) is drawn from a number of observations (so far it has worked every time). This is not very convincing, since if the premise proves to be invalid once, the whole conclusion can be swept off the table.
  2.      With induction, on the basis of a number of observations of a phenomenon, it is assumed that the phenomenon will always occur in this way. In addition, induction provides a "most likely explanation" based on facts.

Take the following for example; "Your partner went to the supermarket this morning and bought lasagne sheets. She also got fresh tomatoes from your grandmother yesterday and you can smell the molten cheese all throughout the house. The inductive reasoning is that you eat lasagne tonight. If you sit down at the table, it appears that you are eating soup tonight. Your partner has been making lasagne for tomorrow because there is little time to cook tomorrow. Your induction was wrong.

The same problem does occur in science. Because the majority of what we know is made up of induction, there is a high chance that incorrect assumptions have been made. This is also regularly proven.

  1.       An argument is always composed of (1) one or more premise (s), and (2) a conclusion.
  2.       The difference between a deductive argument and an inductive argument is that a deductive argument is used to prove a claim, while an inductive argument is used to support a claim.
  3.       An argument is valid when it is impossible that the premises are true and the conclusion false at the same time.
  4.       The three levels are: (1) ethos, (2) logos, and (3) pathos
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