The man in this photo is a police detective. He’s examining and gathering clues that may help solve a murder. Based on all of the clues he finds, he may be able to conclude who committed the crime. Doing science is similar to solving crimes. It also involves gathering evidence and drawing conclusions. Both solving crimes and doing science use inductive reasoning.
What Is Inductive Reasoning?
Inductive reasoning is the process of drawing general conclusions based on many clues, or pieces of evidence. Many crimes are solved using inductive reasoning. It is also the hallmark of science and the basis of the scientific method.
Q: How might the police detective pictured above use inductive reasoning to solve the crime?
A: The detective might gather clues that provide evidence about the identity of the murderer. For example, he might find the bloody shoe print in the Figure below, and this could provide evidence about the size of the murderer. He also might find fingerprints or other evidence left behind by the murderer. The detective might eventually find enough clues to be able to conclude the identity of the most likely suspect.
Inductive Reasoning in Science
A simple example will help you understand how inductive reasoning works in science. Suppose you grew up on a planet named Quim, where there is no gravity. In fact, assume you’ve never even heard of gravity. You travel to Earth (on a student exchange program) and immediately notice things are very different here than on your home planet. For one thing, when you step out of your spacecraft, you fall directly to the ground. Then, when you let go of your communications device, it falls to the ground as well. On Quim, nothing ever falls to the ground. For example, if you had let go of your communications device back home, it would have just stayed in place by your upper appendage. You notice that everything you let go of falls to the ground. Using inductive reasoning, you conclude that all objects fall to the ground on Earth.
Then, you make the observation pictured (Figure below). You see round objects rising up into the sky, rather than falling toward the ground as you expect. Clearly, your first conclusion—although based on many pieces of evidence—is incorrect. You need to gather more evidence to come to a conclusion that explains all of your observations.
Q: What conclusion might you draw based on the additional evidence of the balloons rising instead of falling?
A: With this and other evidence, you might conclude that objects heavier than air fall to the ground but objects lighter than air do not.
Limits on Inductive Reasoning
Inductive reasoning can’t solve a crime or arrive at the correct scientific conclusion with 100 percent certainty. It’s always possible that some piece of evidence remains to be found that would disprove the conclusion. That’s why jurors in a trial are told to decide whether the defendant is guilty “without a reasonable doubt”—not without a shred of doubt. Similarly, a scientific theory is never really proven conclusively to be true. However, it can be supported by so much evidence that it is accepted “without a reasonable doubt.”
- Inductive reasoning is the process of drawing general conclusions based on many pieces of evidence. This type of reasoning is the basis of the scientific method.
- In science, inductive reasoning is used to draw general conclusions from evidence. The conclusions are changed if necessary to explain new evidence as it becomes available.
- Inductive reasoning cannot prove conclusively that an idea is true, but it may lead to conclusions that are very likely to be true.
Deductive reasoning is another type of reasoning. You can think of deductive reasoning as inductive reasoning in reverse. With deductive reasoning, you draw specific conclusions based on general statements that are assumed to be true. At the URL below, read the short article comparing inductive and deductive reasoning. Then put your knowledge into practice by doing the exercises that follow the article.
- What is inductive reasoning?
- Describe how inductive reasoning is used in science.
- Rayna studied rats in a lab. She observed that all 50 rats in her sample preferred to eat brand A rat food and would eat brand B food only when brand A was not available. Can she correctly conclude that all rats prefer brand A rat food over brand B food? Why or why not?