What is Consistency in Logic? | Simple Explanation for Class 6

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What is a Consistency in Logic?

Grade Level:

Class 6

NLP, Law, History, Social Sciences, Literature, Journalism, Communication

Definition

What is it?

Consistency in logic means that all the statements or ideas you are presenting fit together without contradicting each other. If your statements are consistent, they can all be true at the same time. It's like making sure all the pieces of a puzzle fit perfectly.

Simple Example

Quick Example

Imagine your friend tells you, 'I ate two samosas for breakfast.' Later, they say, 'I didn't eat any samosas this morning.' These two statements are inconsistent because they can't both be true at the same time. You either ate samosas or you didn't.

Worked Example

Step-by-Step

Let's check for consistency in a set of statements about a cricket match:

Statement 1: India won the match by 5 wickets.
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Statement 2: The final score was India 250/5 and Australia 245/8.
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Statement 3: Australia batted first and scored 245 runs.
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Statement 4: India chased the target and scored 250 runs, losing 5 wickets.
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Step 1: Check Statement 1 and 2. If India won by 5 wickets, it means they completed the chase with 5 wickets remaining. Statement 2 shows India scored 250/5. This matches.
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Step 2: Check Statement 2 and 3. Statement 2 says Australia scored 245/8. Statement 3 says Australia batted first and scored 245. This matches.
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Step 3: Check Statement 3 and 4. Statement 3 says Australia batted first. Statement 4 says India chased the target. This makes sense.
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Step 4: Check if all statements can be true together. Yes, they all fit perfectly. India won by 5 wickets, chased 245 runs, and scored 250/5. All details align.

Answer: The statements are consistent.

Why It Matters

Consistency is crucial in many fields. In law, lawyers must present consistent arguments to win a case. Journalists need to ensure their news reports are consistent to be credible. Even in everyday conversations, being consistent helps you communicate clearly and avoid misunderstandings, making you a better speaker and writer.

Common Mistakes

MISTAKE: Thinking that if two statements are different, they are automatically inconsistent. | CORRECTION: Statements are inconsistent only if they cannot both be true at the same time. 'I like chai' and 'I like coffee' are different but not inconsistent; you can like both.

MISTAKE: Ignoring context when checking for consistency. | CORRECTION: Always consider the situation or conditions under which statements are made. 'It's raining' and 'It's sunny' are inconsistent if referring to the same place and time, but not if referring to different places or times.

MISTAKE: Believing that consistency means statements must always agree perfectly on every small detail. | CORRECTION: Consistency means there are no direct contradictions that make it impossible for all statements to be true. Slight variations in phrasing are fine as long as the core facts align.

Practice Questions

Try It Yourself

QUESTION: Are these statements consistent? 'My favourite colour is blue.' and 'I love wearing red shirts.' | ANSWER: Yes, they are consistent. You can have a favourite colour but still enjoy wearing other colours.

QUESTION: A shopkeeper says: 'This mobile phone costs Rs. 15,000.' Then he says: 'You can buy this phone for Rs. 14,000 today.' Are these statements consistent? | ANSWER: Yes, they are consistent. The phone's usual price might be Rs. 15,000, but there could be a discount or special offer making it Rs. 14,000 today.

QUESTION: A student says: (1) 'I finished all my homework yesterday.' (2) 'My English homework is due tomorrow, and I haven't started it yet.' Are these statements consistent? Explain why. | ANSWER: No, they are inconsistent. If the student finished ALL homework yesterday, they couldn't have English homework due tomorrow that they haven't started. The second statement contradicts the first.

MCQ

Quick Quiz

Which pair of statements is inconsistent?

My school starts at 8 AM. I reach school by 7:45 AM.

It is hot outside. I am wearing a sweater.

I have two brothers. My family has five members (including me).

The train arrived late. The platform was crowded.

The Correct Answer Is:

Option B is inconsistent because if it's hot outside, wearing a sweater generally doesn't make sense unless there's a specific reason not mentioned. The other options can all be true simultaneously.

Real World Connection

In the Real World

When you read news articles or watch debates on TV, journalists and politicians try to maintain consistency in their arguments and facts. For example, a news channel reporting on an election must ensure all its reports about vote counts or candidate statements are consistent to avoid spreading misinformation and maintain public trust. This is vital in a diverse country like India.

Key Vocabulary

Key Terms

CONTRADICTION: A situation where two statements cannot both be true at the same time. | LOGIC: The study of reasoning and arguments. | CREDIBLE: Able to be believed; trustworthy. | ARGUMENT: A set of reasons or statements given to persuade others.

What's Next

What to Learn Next

Now that you understand consistency, you can explore 'Validity in Logic.' Validity helps us understand if an argument's conclusion follows logically from its premises, building on the idea of statements fitting together correctly.