Induction is one of the three basic types of reasoning. Inductive arguments are those in which a conclusion is drawn about a class of objects, based upon the characteristics observed in a sample. For example, "Most of the jellybeans in my hand are red, and all of the jellybeans in my hand were taken from this jar. So, I infer that most of the jellybeans in this jar are red." The jellybeans in the hand are the sample; the jellybeans in the jar are the target class about which the inference is drawn.

While the meanings of syncategorematic words ('most', 'are', 'so', etc.) is important, the persuasive power of the argument turns chiefly on the extent to which the characteristics of the sample are causally connected to the characteristics of the target class, i.e. that something is causing the characteristics of the sample to more or less accurately reflect the characteristics of the target class. For example, I might have actively stirred or shaken the contents of the jar before taking the sample, thus ensuring that any bean in the jar had an equal chance to be in the sample as any other bean.

Because we can never be sure that a fool-proof causal connection exists between the characteristics of a sample and the characteristics of a target class, an inductive argument cannot guarantee the truth of its conclusion, even assuming that its premisses are true. Hence, inductive reasoning is not as strong as deductive reasoning in terms of the force with which the conclusion follows from its premisses. Inductive reasoning can, at best, give us a measure of probability: it can tell us that a conclusion is probably true. Some really sophisticated inductive arguments can even give us a numerical estimate of how likely we are to be right. But induction is more useful in terms of giving us information about the world around us. Induction can confirm our ideas about the world. What induction cannot do is suggest or introduce new ideas. Induction allows us to confirm or disconfirm what we think, but it cannot make new discoveries.


The Syllogistic Model:

In induction the minor premiss is a CASE, as in deduction--a class subsumed under a rule that we propose to test. This class constitutes the sample. The major premiss of the argument is an OBSERVATION made on the sample. The conclusion is a generalization, or RULE, applying the results of the observation to the target class represented by the sample. For example...

Socrates is mortal.            - An OBSERVATION - if we watch Socrates long enough, he dies.
Socrates is a man.            - A CASE - Socrates is a sample or instance representing the class 'men'.
So, all men are mortal       - A RULE about men.


Critique of Inductive Reasoning:

Since the persuasive power of inductive reasoning turns upon the strenth of the causal connection between the characteristics of the sample and the characteristics of the target class, inductive arguments can be strengthened by improving that causal connection, or weakened by undermining that connection. The connection is established by two factors: the care with which the observations are made (to enhance their accuracy), and the care with which the sample is drawn (to enhance its representativeness).

In addition, inductive reasoning, like the other forms of reasoning, is subject to a variety of fallacies. An inductive fallacy occurs when the causal connection that warrants the inductive inference from sample to target population is so weak that the argument must be rejected as worthless.


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