You are correct that the sentences can be interpreted in different ways. Let's break them down:
a. "I do not believe that anything he saysis true."
This sentence implies that the person believes everything the speaker says is false. It does not leave room for any exceptions.
b. "I don't believe anything he says."
This sentence could be interpreted in two ways:
- The person doesnis true." This sentence could have two interpretations:
- The speaker does not believe that any statement made by the person in question is true.
- The speaker is expressing severe skepticism towards everything the person says, implying that the majority or all of the person's statements are likely false.
b. "I don't believe anything he says." This sentence can similarly be interpreted in two ways:
- The speaker does not believe any individual statement made by the person in question.
- The speaker is expressing a more general lack of trust in the person, suggesting that nothing they say can be taken at face value.
Without additional context, it's difficult to determine the intended meaning of these sentences.