Inductive Reasoning Help

Introduction to Inductive Reasoning

"A man who does not think for himself does not think at all."

—Oscar Wilde, Irish playwright, poet, and author (1854–1900)

Lesson Summary

In this lesson, you'll review the difference between deductive and inductive reasoning. You'll also sharpen your inductive reasoning skills by learning how to draw logical conclusions from evidence.

The lesson Inductive vs Deductive Reasoning Help explains the difference between inductive and deductive reasoning. In deductive reasoning, as you know, an argument moves from a conclusion to the evidence (premises) that supports that conclusion. Inductive arguments, on the other hand, move from evidence to a conclusion drawn from that evidence.

As a critical thinker, when you come across a deductive argument, you should examine the validity of the evidence for the conclusion. If the evidence is valid, the conclusion—and therefore the whole argument—is a good one. However, in inductive reasoning, the goal is not to test the validity of the evidence. Rather, it is to examine the validity of the conclusion. If the conclusion stems logically from the evidence, then the argument can be considered a good one.

But how do you know if the conclusion is logical? In inductive reasoning, the main criterion is to determine the likelihood that the premises lead to the conclusion. Likelihood can be judged based on:

1. Common sense
2. Past experience

Of course, formal logic, involving mathematical symbols, can also help, but that won't be discussed in this book.

Here's an example of a brief inductive argument:

Due to a storm, there was a major power-outage last night in a nearby town. A lot of people must have used flashlights and lit candles to see.

If the premise that there was a major power-outage in a nearby town is true, is it reasonable to assume that a lot of people lit candles and used flashlights to see? What do you think—is a power-outage at night likely to cause people to turn on flashlights and light candles? Based on common sense and past experience, you can say with confidence yes. Is it very likely? Again, you can confidently say yes. Therefore, this is a good inductive argument—a logical conclusion drawn from common sense and past experience; or substantial evidence.

The Science of Inductive Reasoning

Any time someone draws conclusions from evidence, inductive reasoning is being used. Scientists use it all the time. For example, let's say a scientist takes two equally healthy plants of the same size, age, and type. She puts Plant A in a room with a radio that plays only classical music. She puts Plant B in a room with a radio that plays only rock and roll. Both plants receive equal light and water. After six weeks, Plant A has grown six inches. Plant B, on the other hand, has grown only three inches, which is the average growth rate for these types of plants. She repeats this experiment and gets the same results. Using her inductive reasoning skills, what is the most logical thing for the scientist to conclude?

1. In both cases, Plant B must not have been as healthy to start as Plant A.
2. Plants grow better when exposed to classical music than to rock and roll.
3. Rock and roll music stunts plant growth.

Well, common sense would suggest that choice a isn't an option, because it is stated that both plants were equally healthy at the start of the experiment. Furthermore, since it is known that Plant B grew at the normal rate, then c can't be a logical conclusion either. But even without this process of elimination, common sense and the results of the two experiments point to conclusion b, that plants grow better to classical music than to rock and roll. (This is true, by the way!)

Of course, this conclusion would be even more valid if the scientist repeated the experiment several more times and continued to get the same results. The more she performs the experiment and gets the same results, the stronger her argument will be.

Tip

Many of the concepts in reasoning and logic are also used in different mathematical concepts. With inductive reasoning, you can think of it as a type of formula with Logical conclusion = common sense + past experience + substantial evidence