Today I had a question about why this group of sentences is not correct:
Lindsay had better call me tonight, but that is not okay if she doesn’t. I cannot talk to her tomorrow.*
To the ears of a native English speaker, the above group of sentences sounds strange. The question is why does this group of sentences sound strange. I think the main reason is because of the word “but”. If the word “but” is removed from the group of sentences, then it sounds okay.
Lindsay had better call me tonight. That is not okay if she doesn’t. I cannot talk to her tomorrow.
This new version is perfectly acceptable. Why then is this not correct with the word “but”?
The word “but” in this case is a coordinating conjunction. It joins together to sentenceds. The coordinating conjunction “but” can be used to indicate that two sentences contain opposite or contrasting ideas. “But” can also be used to give a sense a conflict between two sets of ideas, or a sense of negation between two sets of ideas.
The first idea in the example above is “Lindsey had better call me tonight”. The use of the modal “had better” conveys a sense of warning, and implies that something bad may happen if Lindsey does not call.
The second idea in the example above is “That is not okay if she doesn’t [call]. I cannot talk to her tomorrow.”
Does the first idea contrast or conflict with the second idea? Does the second idea negate the first idea? Is the first idea the opposite of the second idea? The answer to all three of these questions is no. The second idea is more of an explanation of the first idea. As a result, the coordinating conjunction “but” doesn’t fit with this group of sentences.