Skip Nav

# Deduction & Induction

❶But in any event, you are the only one who can decide whether an inductive or deductive approach is appropriate for your research project. The Research Council of Norway.

## Inductive vs. Deductive Reasoning

For example, weather forecasting is an area where deductive reasoning probabilities are often used. A meteorologist will look at the data, and using their skill and judgment, decide upon the likely weather for that day. They are aware that a certain pattern of initial conditions frequently leads to a certain weather type. However, they will never say that it is definitely going to rain, because the weather is too unpredictable, and they can never be sure that their initial assumptions are correct.

Michael Fish, the respected British meteorologist, categorically stated in that there was no chance of a hurricane hitting Southern England.

He was wrong, and the unprepared country was devastated. The initial premises of his deductive reasoning were wrong. These days forecasters always warn of adverse weather as a percentage chance, affording people the choice of preparing for the worst. Check out our quiz-page with tests about:.

Check out our quiz-page with tests about: Back to Overview "Reasoning". Search over articles on psychology, science, and experiments. Leave this field blank: Modus ponens also known as "affirming the antecedent" or "the law of detachment" is the primary deductive rule of inference. The argument form is listed below:.

Such an argument commits the logical fallacy of affirming the consequent. It might be true that other angles outside this range are also obtuse. Modus tollens also known as "the law of contrapositive" is a deductive rule of inference. In contrast to modus ponens , reasoning with modus tollens goes in the opposite direction to that of the conditional. The general expression for modus tollens is the following:.

The law of syllogism takes two conditional statements and forms a conclusion by combining the hypothesis of one statement with the conclusion of another. Here is the general form:. We deduced the final statement by combining the hypothesis of the first statement with the conclusion of the second statement.

We also allow that this could be a false statement. This is an example of the transitive property in mathematics. Another example is the transitive property of equality which can be stated in this form:. Deductive arguments are evaluated in terms of their validity and soundness. In other words, the conclusion must be true if the premises are true. It is possible to have a deductive argument that is logically valid but is not sound. Fallacious arguments often take that form.

In other words, it is impossible for the premises to be true and the conclusion false. False generalizations — such as "Everyone who eats carrots is a quarterback" — are often used to make unsound arguments. The fact that there are some people who eat carrots but are not quarterbacks proves the flaw of the argument.

In this example, the first statement uses categorical reasoning , saying that all carrot-eaters are definitely quarterbacks. This theory of deductive reasoning — also known as term logic — was developed by Aristotle , but was superseded by propositional sentential logic and predicate logic.

Deductive reasoning can be contrasted with inductive reasoning , in regards to validity and soundness. Aristotle started documenting deductive reasoning in the 4th century BC. From Wikipedia, the free encyclopedia. This section needs expansion. You can help by adding to it. Logic portal Web portal.

## Main Topics

A deductive approach is concerned with “developing a hypothesis (or hypotheses) based on existing theory, and then designing a research strategy to test the hypothesis”[1] It has been stated that “deductive means reasoning from the particular to the general. If a causal relationship or link.

### Privacy FAQs

In logic, we often refer to the two broad methods of reasoning as the deductive and inductive approaches. Deductive reasoning works from the more general to the more specific. Sometimes this is informally called a "top-down" approach.