Logic is the study of reasoning and principles that determine valid arguments and correct thinking. It is foundational to philosophy, mathematics, and computer science. Here are the basics:
1. Propositions
A proposition is a declarative statement that can be either true or false, but not both. Examples:
"The sky is blue." (true)
"2 + 2 = 5." (false)
2. Logical Connectives
Logical connectives combine or modify propositions. Common connectives include:
AND (∧): True if both propositions are true.
Example: "It is raining AND it is cold."
OR (∨): True if at least one proposition is true.
Example: "It is raining OR it is sunny."
NOT (¬): Negates a proposition (true becomes false, and vice versa).
Example: "NOT raining" means "It is not raining."
IF...THEN (→): True unless the first proposition is true and the second is false.
Example: "If it rains, then the ground is wet."
IF AND ONLY IF (↔): True if both propositions are either true or false.
Example: "You win IF AND ONLY IF you score the most points."
3. Arguments
An argument consists of premises (statements) and a conclusion. The goal is to determine whether the conclusion logically follows from the premises.
Example:
Premise 1: All humans are mortal.
Premise 2: Socrates is a human.
Conclusion: Socrates is mortal.
4. Validity and Soundness
An argument is valid if the conclusion logically follows from the premises, regardless of whether the premises are true.
An argument is sound if it is valid and its premises are true.
5. Types of Logic
Deductive Logic: Reasoning from general principles to specific conclusions. If valid, the conclusion must be true.
Inductive Logic: Reasoning from specific cases to general principles. It provides probable, but not certain, conclusions.
Formal Logic: Focuses on the structure of arguments using symbolic representations.
Informal Logic: Deals with everyday reasoning and argumentation.
6. Fallacies
Fallacies are errors in reasoning that lead to invalid arguments. Examples include:
Ad Hominem: Attacking the person instead of their argument.
Straw Man: Misrepresenting an argument to make it easier to attack.
Logic helps us evaluate arguments, make decisions, and think critically. Understanding its basic principles enables clearer and more precise reasoning.
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