Disjunctive syllogism

Disjunctive Syllogism is a fundamental form of logical argument in the field of Philosophy and Logic that allows one to deduce a conclusion from two contradictory premises. It is a type of Syllogism, which is a form of reasoning where a conclusion is drawn from two given or assumed propositions (premises). A disjunctive syllogism, specifically, involves a disjunction (an "either/or" statement) as one of its premises.

Definition

A disjunctive syllogism follows the basic structure:

1. Either A or B is true. 2. A is not true. 3. Therefore, B must be true.

Alternatively, it can be presented as:

1. Either A or B is true. 2. B is not true. 3. Therefore, A must be true.

In this logical structure, the first premise presents two options, one of which must be true. The second premise negates one of these options. Consequently, the conclusion affirms the truth of the remaining option.

Examples

Consider the following example to illustrate disjunctive syllogism:

1. Either the light is on or the light is off. 2. The light is not on. 3. Therefore, the light is off.

This example clearly demonstrates how disjunctive syllogism allows for a conclusion to be drawn based on the negation of one of the two possible states.

Application

Disjunctive syllogism is widely used in various fields such as Mathematics, Computer Science, and Philosophy for problem-solving and decision-making processes. It is particularly useful in algorithms and programming for making decisions between two options based on the negation of one option.

Criticism and Limitations

While disjunctive syllogism is a powerful tool in logic, it is not without its criticisms and limitations. One limitation is that it relies on the assumption that the initial disjunction is exhaustive, meaning that no other options exist beyond those presented. If this assumption is not true, the conclusion drawn may be incorrect.

See Also

• Syllogism
• Logic
• Philosophy of Logic
• Deductive Reasoning
• Inductive Reasoning