Deductive, Inductive & Hypothetical-Deductive Reasoning in Science

Deductive Method

This method consists in going from general statements to particular statements. From some general judgments or definitions, individual conclusions, that are the necessary consequence of the first, are deduced.

The consistency and validity of this method is unquestionable: if the premises are true, the conclusion will be true as well.

This method is characteristic of formal sciences, although in empirical sciences it is also used in the first part of the investigation, when it is necessary to formulate hypotheses. This method is only feasible and sufficient in the formal sciences. For that reason, it is considered an inadequate method because, although it is useful to construct valid arguments,

Inductive Method

This method starts from particular experiences or statements to formulate a general conclusion. A scientist, after observing that a property or event is repeated in many individual cases, concludes that such property belongs to all individuals of the same type. This general statement is considered as a law. Therefore, this method has been frequently used in the empirical sciences.

Advantages of the Inductive Method:

• It provides principles or laws applicable to all similar events.

Problems of the Inductive Method:

• It is questionable that the scientific procedure begins with neutral observation.
• The concept of "observation" is problematic because, in modern science, what we call "observation" is often interfered by technology.
• The validity or reliability of the reached principles by means of induction is also questionable. No matter how many cases we have checked and no matter if they have been very well selected, nothing assures us that all the other possible cases are of the same type and, even less, that future cases are going to also follow the same pattern.

Hypothetical-Deductive Method

This method combines the reference to empirical data obtained from induction and the generality and consistency of the deduction.

Steps of the Hypothetical-Deductive Method:

1. Definition of the Problem

This step starts from the detection of a problematic fact, that is, an event that cannot be explained by means of current theories or contradicts some principles of our current theories.

2. Formulation of the Hypothesis

A possible explanation is proposed, but it must be coherent and consistent with the scientific attitude.

3. Deduction of Consequences

Using the deductive method, we extract the consequences of the hypothesis, if it were true.

4. Validation of the Hypothesis

This process checks whether or not our hypothesis accomplishes the expected consequences. It is necessary to resort to empirical observation of reality. Therefore, it is an inductive step.

However, because of the fact we cannot verify all cases, we can check the validity of the hypothesis from a sufficient number of carefully selected cases.

5. Confirmation or Refutation of the Hypothesis

• Refutation: One hypothesis is refuted when the expected consequences are not achieved.
• Confirmation: One hypothesis is confirmed when the expected consequences are accomplished.