As previously discussed, arguments are made for different reasons. While deductive arguments attempt to prove that something is absolutely certain, deductive reasoning is not the only way people understand the world. Other arguments focus on what is probably true, and knowledge gathered this way is called inductive reasoning.
While deductive arguments start with broad concepts and then zoom in to reveal specific truths, inductive arguments work in reverse—they take a number of specific cases to draw a general conclusion that can be held with a reasonable degree of certainty.
|Deductive arguments are those that offer certainty. They usually use general premises to draw a specific and logically necessary conclusion.||Inductive arguments use two or more premises to support a tentative conclusion. They usually start with specific observations that combine to give reasonable certainty to a general conclusion.|
The type of thinking found in inductive arguments usually looks something like this:
Every time I have kept a gallon of milk in my fridge for more than a month after the expiration date, it has gone sour.
That gallon of milk has been in my fridge for over a month after the expiration date.
Therefore, that gallon of milk has probably gone sour.
The effect of milk going sour has happened so repeatedly that it is a reasonable speculation to assume that it will be sour again this time as well.
As with all arguments, some inductive arguments are better than others. But inductive arguments cannot be subjected to the same kind of tests for validity that we use for deductive arguments. The categorical claims of deductive arguments tend to make them decisively true or false. Things are fuzzier when using inductive arguments, and the argument’s strength relies on the quality of the evidence used.
The argument above seems fairly strong, largely because your personal experience probably matches up with the experience of the person doing the reasoning. The following argument is much weaker:
Marcus is an engineering student who wears glasses.
Lauren is an engineering student who wears glasses.
Therefore, all engineering students wear glasses.
Two instances do not create a high probability that the quality of wearing glasses apply to all engineering students.
· A large, diverse, and bias-free sample size of examples leading to the conclusion
· A high percentage of instances that fit the conclusion
· An analogy in which the items being compared are similar in relevant ways
The scientific method relies heavily on inductive reasoning. If you observe that water freezes every time you lower its temperature to 32 degrees, you can make an inductive argument that the freezing temperature of water is strictly 32 degrees. As more people try this in more places with more diverse conditions, the strength of the argument increases.
At its strongest, the argument simply states that water freezes at 32 degrees. However, there’s no way to prove that this is really true in all circumstances in all places. We’re generalizing—or using inductive reasoning—based on many tests. This knowledge can be quite reliable, but it’s not necessarily or categorically true in the way that a deductive argument is.
Answer the following questions about the material above.
Which of the following is a true statement about inductive reasoning?
· Inductive arguments do not need to offer support for their conclusions.
· Inductive arguments reach definite conclusions.
· Inductive arguments do not have conclusions.
· Inductive arguments reach probable conclusions.
Your friend recommends her favorite mystery author, so you pick up one of the author’s books at the bookstore. You’re hooked, and before long you’ve read all nine of the author’s published novels. The plots vary, but you notice that eight of the nine novels have a male protagonist and take place in the American South. When the author’s tenth book comes out, you could use inductive reasoning to come to which of the following conclusions?
· The book will definitely not have a male protagonist or take place in the American South.
· The book will definitely have a male protagonist and take place in the American South.
· The book will probably have a male protagonist and take place in the American South.
· The book will probably not have a male protagonist or take place in the American South.
Craig is a college student claiming that he took a survey and is confident that the vast majority of students at his school vote in primary elections. Craig’s claim would be MOST persuasive if you knew he obtained his information in which of the following ways?
· Craig surveyed every third person to walk into the student union during peak hours over the course of several days.
· Craig put up a flier in the political science department asking people to email him their responses.
· Craig surveyed everyone in his fraternity, and told his friends to ask their friends.
· Craig surveyed the first eight people he bumped into at a football game.
Suppose you read a study that stated that 52 percent of all voters in the town of Marble Glen are registered Democrats. Now consider the following argument:
The majority of voters in Marble Glen are Democrats.
Fiona lives in Marble Glen.
Therefore, Fiona is probably a Democrat.
How strong or weak is this inductive argument? Explain your answer.
Arguments / 3.6 Practice: Induction Questions: 0 of 6 complete (0%) | 0 of 4 correct (0%)