Final answer:
The idea is that if a sentence is meaningless, then its negation is also meaningless.
Step-by-step explanation:
The idea that if a sentence is meaningless, then its negation is also meaningless is related to the law of noncontradiction. The law of noncontradiction states that a statement and its negation cannot both be true at the same time. This applies to both meaningful and meaningless sentences. For example, if we have a meaningless sentence like 'Colorless green ideas sleep furiously,' its negation would also be meaningless.
In English grammar, we recognize meaningful sentences based on the rules of syntax and semantics. If a sentence follows these rules and conveys a coherent meaning, it is considered meaningful. However, if a sentence violates these rules or does not make sense, it is considered meaningless. In such cases, its negation (opposite statement) would also lack meaning.
For instance, the sentence 'The sky is not blue and it is not not blue' is grammatically incorrect and does not convey a coherent meaning. Therefore, its negation 'The sky is blue and it is not not blue' would also be grammatically incorrect and meaningless.