KNOW THE ELEMENTARY RULES OF REASONING

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Course: Philosophy, Logic and Human Existence
Book: KNOW THE ELEMENTARY RULES OF REASONING
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Date: Saturday, 6 June 2026, 6:51 PM

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1. KNOW THE ELEMENTARY RULES OF REASONING

Reasoning is defined as the process of thinking in a structured and logical way to reach conclusions.

Here are some elementary rules of reasoning, foundational in logic, philosophy, and everyday critical thinking. These help in drawing valid conclusions and evaluating our arguments:

1.     Law of Identity

Rule: A is A

Explanation: Everything is identical to itself. If something is true, then it's true.

Example: If "snow is white" is true, then "snow is white" remains true.

2.     Law of Non-Contradiction

Rule: A proposition cannot be both true and false at the same time in the same sense.

Example: "It is raining" and "It is not raining" cannot both be true at the same time and place.

3.     Law of the Excluded Middle

Rule: Either a proposition is true, or its negation is true.

Example:  "The light is on" is either true or false—there is no middle option.

4.     Modus Ponens (Direct Inference)

Modus Ponens is a fundamental rule of logic used in deductive reasoning. The name comes from Latin and means "method of affirming."

Modus Ponens has the following logical structure:

1.       If P, then Q.                       (conditional statement)

2.       P is true.           (affirming the antecedent)

3.       Therefore, Q is true.        (conclusion)

Example:

If it rains, the ground will be wet.

It is raining.

Therefore, the ground is wet.

This is a valid form of argument and is widely used in mathematics, philosophy, and computer science.


2. KNOW THE ELEMENTARY RULES OF REASONING

5.     Modus Tollens (Denying the Consequent)

Modus tollens is a valid form of logical argument (also called a rule of inference) used in deductive reasoning. The structure is:

If P, then Q.

Not Q.

Therefore, not P.

Example:

If it is raining, then the ground is wet.

The ground is not wet.

Therefore, it is not raining.

Modus tollens allows you to conclude that the initial condition (P) is false because the expected result (Q) did not occur

6.     Hypothetical Syllogism

Hypothetical syllogism is a logical argument that uses conditional ("if-then") statements to deduce a conclusion from two premises. It's a form of deductive reasoning commonly used in propositional logic.

          Both premises and the conclusion are conditional statements.

          Structure:

          If P, then Q.

          If Q, then R.

            ∴ If P, then R.

Example:

          If I study, then I will pass the exam.

          If I pass the exam, then I will graduate.

          Therefore, if I study, then I will graduate

7.     Disjunctive Syllogism

Disjunctive syllogism is a valid form of logical argument that follows this structure:

Either A or B is true. (A ∨ B)

A is not true. (¬A)

Therefore, B must be true. (∴ B)

Example:

Either it is raining or it is snowing.

It is not raining.

Therefore, it is snowing.

This type of reasoning is used to eliminate possibilities and conclude what must be true when given a limited set of options.


3. Avoiding Logical Fallacies

Argumentum ad hominem is a Latin term meaning "argument to the person." It refers to a rhetorical strategy where an individual attacks the character, motive, or other attributes of the person making an argument, rather than addressing the substance of the argument itself. This approach is considered a logical fallacy, specifically a fallacy of relevance, because it diverts attention from the actual issue being discussed

FORMS OF AD HOMINEM

1.     Argumentum ad baculum, is a logical fallacy that occurs when someone uses a threat of force or negative consequences to persuade others to accept a conclusion, rather than providing logical reasoning or evidence. This type of argument appeals to fear or coercion, aiming to compel agreement through intimidation rather than rational discourse.

Characteristics Of Argumentum Ad Baculum

·        Appeal to Fear or Threat: The argument relies on the audience's fear of negative consequences rather than on logical reasoning.

·        Lack of Logical Connection: There is no logical link between the threat presented and the conclusion being advocated.

·        Coercive Persuasion: The argument seeks to force acceptance of a conclusion through intimidation.

Examples

1.       "If you don't support this policy, you'll lose your job."

2.       "Agree with our demands, or face legal action."

3.       "Believe in this doctrine, or suffer eternal punishment

Fallacious Nature

Argumentum ad baculum is considered fallacious because it substitutes a threat for actual evidence supporting the conclusion. The validity of a claim should be based on logical reasoning and factual.        

Elements of a Good Argument

Clarity: Terms must be clearly defined.

Relevance: Premises must directly relate to the conclusion.

Consistency: No contradictions in reasoning.

Soundness: (for deductive arguments): True premises and valid structure.

Cogency (for inductive arguments): Strong reasoning with reliable evidence, not on the potential consequences of disagreement

PRACTICAL APPLICATION

Apply reasoning in:

Problem-solving

Decision-making

Academic writing

Everyday conversations

Critical reading and analysis