Logical Deduction
Deduction means deriving new, necessarily true statements from existing statements (premises). This is the foundation of logical reasoning.
What is the Essence of Deduction?
- If the initial statements are true, the conclusion must also be true.
- Deduction is based on formal rules, not content.
- This ensures that the reasoning is always valid.
Simple Example
- Premise 1: "All humans are mortal."
- Premise 2: "Socrates is human."
- Conclusion: "Socrates is mortal."
This is a classic deductive argument: the conclusion is necessarily true if the initial statements are true.
Formal Notation
This means: from premises P1, P2, …, Pn, conclusion Q can be derived. The ⊢ symbol denotes logical derivation.
Deductive Validity
A conclusion is deductively valid if it is impossible for the premises to be true and the conclusion false.
Summary
Deduction is a conclusion in which a necessarily true conclusion follows from true premises. This is the basis of proofs in mathematics and logic.
Practice Exercise
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