inductive argument

What is an inductive argument?

An inductive argument is an assertion that uses specific premises or observations to make a broader generalization. Inductive arguments, by their nature, possess some degree of uncertainty. They are used to show the likelihood that a conclusion drawn from known premises is true.

Logic plays a big role in inductive arguments. In these arguments, the conclusion is supported by information that is known to be true or could be true in the future. Another way of saying this is that the truth of the premises supports the truth of the conclusion. The goal is to arrive at the most likely conclusion or the strongest possible explanation, given a set of circumstances and observations.

Inductive arguments -- also known as reasoning by induction -- are assessed as strong or weak, rather than as valid or invalid. In a strong inductive argument, if the premises are true, it would be highly unlikely that the conclusion would be false. A strong inductive conclusion contains reliable beliefs that are backed by strong evidence (even though there is no guarantee that the beliefs are indisputable). But if an inductive argument is weak, the logic between the premises and the conclusion would be incorrect, indicating weak beliefs and a possible unsound conclusion.

Inductive arguments vs. deductive arguments

Both inductive and deductive arguments are based on logic, facts and evidence. Where they differ is that an inductive argument is a type of bottom-up logic because it aims to widen specific premises into a broader generalization. In contrast, a deductive argument is a top-down argument that produces an irrefutable conclusion (as long as its premises are true).

When making an inductive argument, the arguer uses logic to establish a conclusion that is most likely to be valid, based on the given facts. But in a deductive argument, the arguer's goal is to provide a conclusion that guarantees the truth. Thus, the conclusion of a deductive argument is either true or false, provided that its premises are true. It cannot be partly valid or partly invalid, so there is no possibility of doubt. So, if the premises are known to be true, it's impossible for the conclusion of a deductive argument to be false.

When the premises guarantee the conclusion, the deductive argument is said to be deductively valid or sound. In contrast, the conclusion of an inductive argument is evaluated using terms like strong or most likely.

Inductive arguments with examples

The following example illustrates how an inductive argument uses specific facts to make a broader conclusion:

• Premise: All the tigers I saw on my safari trip to South Africa were orange.
• Conclusion: Therefore, all tigers are orange.

This is an example of a weak inductive argument because even though the premise is true (the observer saw only orange tigers on their trip), the conclusion cannot be true. This is because white tigers also exist, even though the observer didn't see them.

It is possible to strengthen this inductive argument and its conclusion:

• Premise: All the tigers I saw on my safari trip to South Africa were orange.
• Conclusion: Hence, most tigers are probably orange.

Although the conclusion is not 100% true (white tigers still do exist), it is much stronger than the previous argument due to the words most and probably.

Applications of inductive reasoning

Almost everyone uses inductive reasoning every day to make sense of the world and to communicate their opinions and conclusions to others. Inductive arguments are also the foundation of scientific observations and research experiments. Scientists and researchers gather data, create hypotheses based on that data and then test their theories to prove or disprove those hypotheses.

Inductive arguments are also used frequently and very effectively in academia and in the practice of law. In fact, lawyers almost always use inductive arguments and provide evidence that seems irrefutable to support those arguments. Their reasoning is aimed at establishing a logical relationship between known facts. They are able to draw a strong conclusion and support it with the available evidence.

Depending on the strength of the lawyers' arguments and the validity of the evidence they present, the listener (such as the judge or jury) will assess which argument is sound and which one is unsound. These factors determine whether the defense or prosecution will win the case.

Types of inductive reasoning

There are many types of inductive arguments, such as the following:

Generalized reasoning

A generalized inductive argument uses premises about a sample set to draw general conclusions about a larger population. The tiger example from the earlier section is an example of a generalized inductive argument.

Example

• Premise: The right-handed musicians I have seen play right-handed guitars.
• Conclusion: All right-handed musicians probably play right-handed guitars.

Statistical generalization

In this type of argument, statistics based on a large (and usually random) sample set are used to support conclusions. Since the statistics are quantifiable and not vague or unsupported, such generalizations usually strengthen the conclusion.

Example

• Premise: Worldwide, about 2% of people are born with red hair.
• Conclusion: A randomly selected person probably won't have red hair.

Causal inference

A causal argument creates a causal (cause-and-effect) link between the premise and the conclusion.

Example

• Premise: All the sweets in this box are doughnuts. I just saw a jam-filled doughnut.
• Conclusion: Therefore, all the doughnuts in the box are probably jam-filled.

Bayesian reasoning

In Bayesian reasoning, statistical reasoning -- simply put, probability -- is used to account for additional or new information. This kind of inductive argument is frequently used in statistics, as well as the following areas:

• law
• engineering
• medicine
• science
• sports

Analogical or analogous reasoning

The arguer concludes that because two groups have some shared property or similarity, they are also likely to share another property or similarity.

Example

• Premise: John and Will are left-handed and pitch left-handed. Bob is also left-handed.
• Conclusion: Hence, Bob is likely to be a left-handed pitcher.

Predictive reasoning

As its name suggests, a predictive inductive argument involves making some prediction about the future. Thus, a conclusion is drawn based on previously known or past information.

Example

• Premise: I have always seen sunflowers bloom in summer in this valley.
• Conclusion: Therefore, I will see sunflowers bloom in this valley next summer.

Drawbacks of inductive arguments

An inductive argument is not capable of delivering a binary, true-or-false conclusion. This is because such arguments are often based on circumstantial evidence and a limited number of samples. Because of this limitation, an inductive argument can be disproven by a single negative or weak sample.

Inductive reasoning is also susceptible to failures because of cognitive bias, which occurs when the investigator only sees what they expect to support their argument. This may result in a weak argument or unsound conclusion and make the listener doubt the reliability of the arguer's beliefs.

Inductive arguments can be convincing and show that a conclusion is likely to be true. However, they do not provide absolute proof.