Kupas Tuntas LOGIKA dalam 13 Menit

Main ideas / lessons

• “Logic/logical” is used with multiple meanings, and people often mix them up when answering logic questions.
• In everyday Indonesian/English conversation, “logical” commonly means “makes sense” or “reasonable” (based on what seems plausible).
• In formal logic (including mathematical logic), “logical” means the conclusion follows from the premises according to valid rules—not whether it matches real-world facts.
• There is also a broader dictionary meaning where “logic” can mean a person’s “reasoning system” or “rule-based thinking”, such as moral or legal reasoning.

Concepts explained through examples

1) Everyday meaning: “reasonable / makes sense”

A premise like “Keeping a ngepet pigs can make you rich” leads people to ask:

• Is it reasonable?
• Is it true in reality?

People may answer “logical” or “illogical” depending on:

• whether they think the myth has proof / matches real facts, or
• whether the reasoning “sounds believable.”

Key clarification The speaker argues that “logical” in casual speech is often conflated with “true/false in reality,” which is different from formal logic.

2) Formal logic meaning: “valid deduction from premises”

In formal logic, the core requirement is:

• If premises are accepted, the conclusion must be true by the rules of reasoning.

Example structure given:

• Premise: “If you keep a piggy bank, you will be rich.”
• Premise: “Upin keeps a piggy bank.”
• Conclusion: “Upin is rich.” → This is described as logical (valid in formal logic).

Contrast:

• If the conclusion is “Upin is not rich,” then it violates the logic rules based on premises → not logical.

Another example: universal quantifier / set reasoning

• Premise: “All people with hair are women.”
• If you are told someone is hairy, then under that rule you can conclude they are a woman.
• If you are told someone is not a woman, then under that rule they cannot be hairy.

The point is that formal logic uses the premises and the formal rules, not whether humans in real life match the premise.

Common misunderstanding the speaker addresses

A viewer’s comment like “How can we answer logically?” is explained as confusion between:

• real-world categories (“men can have hair too”), and
• the formal logic task (does the conclusion follow from the given premises as stated).

3) General/dictionary meaning: “reasoning framework” (moral/legal)

The speaker gives examples where “illogical” is used to mean:

• morally wrong reasoning, or
• wrong procedure in law-making, etc.

Example (moral debate)

• A person kidnaps their own child.
• Netizens say it is illogical because it violates a moral rule such as:
  • “All kidnapping is wrong.”
• So “illogical” reflects reasoning that clashes with accepted moral norms.

Example (legal debate)

• People argue about whether a law cancellation/creation follows legal procedure.
• “Rules” here mean procedurally regulated norms in law.

Deductive vs inductive logic (methodology / instruction-style)

The speaker contrasts how conclusions should be drawn depending on whether the task is deductive formal logic or empirical/pattern-based reasoning.

Deductive formal logic (what formal logic questions require)

• Use only the provided premises and apply deductive rules.

Example given:

• Premise 1: If it rains, the road is wet.
• Premise 2: The road is wet.
• Conclusion proposed: Rain.

The speaker explains why this is not valid deductively:

• From “If raining → wet,” you cannot infer “wet → raining” just from the road being wet.
• The premise “road is wet” does not uniquely determine that rain occurred.

Deductive reasoning should only allow conclusions that follow strictly from premise structure.

Inductive reasoning (what some answerers do instead)

Instead of formal deduction, use real-world patterns:

• “When the road is wet, usually it’s because it rained.”

So someone might say “Therefore it rains” based on frequency/likelihood rather than deductive necessity.

The speaker emphasizes that the problem being discussed is in the realm of formal (deductive) logic, so inductive answers are treated as incorrect for that task.

Why the speaker explains “logic” vs “logical”

• The goal is to reduce communication confusion:
  • People may be talking past each other because they use different meanings of “logic/logical.”
• The speaker argues that for formal logic exercises, arguments about whether the real world matches the premise are irrelevant.
• The test is whether you can produce a valid deductive conclusion from the given premises.

Speakers / sources featured

• Speaker: The video’s narrator/author (no name provided in the subtitles).
• Sources/Citations: Mentions dictionaries and general reference to formal logic / mathematical logic (no specific dictionary or external author named).