In English, modal verbs like ‘ought to’ and ‘can’ express different levels of certainty, obligation, and ability. Understanding when to use ‘ought to’ versus ‘can’ is essential in choosing the right expression for specific contexts. In this article, we’ll break down the sentence from the question and explain why ‘ought to have arrived’ is correct, while ‘can arrive’ is not.
Understanding the Sentence Structure
The sentence in question is: ‘My sister ( ) here by now, for she took the early train.’ The blank is asking for a modal verb that correctly conveys the idea that her arrival should have happened by now, based on the information that she took the early train. This is a situation that involves expectations and past possibilities, not simple present ability.
In this case, the appropriate choice is ‘ought to have arrived.’ This construction implies that, given the circumstances (taking the early train), the sister was expected to arrive by now, but hasn’t yet. The past perfect ‘have arrived’ indicates that this expectation is set in the past, looking at a moment that should have already happened.
Why ‘Ought to Have Arrived’ is Correct
‘Ought to’ is a modal verb that expresses an expectation or obligation. In this context, ‘ought to have arrived’ conveys that it was expected or required that the sister should have arrived by now, but she has not. The construction ‘ought to have + past participle’ is used when you want to indicate that something should have happened in the past, but it did not.
For example, ‘She ought to have finished her homework by now’ means that the expected action (finishing homework) should have been completed at the current point in time, but the action did not occur as expected.
Why ‘Can Arrive’ is Not Suitable
‘Can’ is a modal verb used to express ability or permission. The sentence ‘My sister can arrive here by now’ would imply that it is possible for her to arrive by now, but it doesn’t communicate the idea that she was expected to have arrived. It suggests an ability or potential rather than an expectation based on the early train. This changes the meaning entirely, making it inappropriate in this context.
Using ‘can’ would be used if you were discussing her ability to arrive now or in the future, not a past expectation based on her taking the early train. For example, ‘She can arrive tomorrow’ suggests a possibility in the future, not a past expectation.
Modal Verbs and Their Different Uses
Modal verbs such as ‘ought to,’ ‘should,’ ‘can,’ ‘could,’ and ‘must’ are often confused, but each has its specific use. Here’s a brief overview of when to use some common modal verbs:
- Ought to/Should: These express an expectation, advice, or obligation, often in the past or present (e.g., ‘You ought to study more’).
- Can: This is used to express ability or possibility (e.g., ‘I can speak French’).
- Must: This shows necessity or strong obligation (e.g., ‘You must wear a helmet’).
Conclusion
The confusion between ‘ought to have arrived’ and ‘can arrive’ comes down to the difference in their meanings. ‘Ought to have arrived’ reflects an expectation about a past action that should have been completed, while ‘can’ implies present ability or possibility. To convey the idea that something was expected but has not yet happened, ‘ought to have arrived’ is the correct choice. Understanding these nuances in modal verb usage is crucial for clear and accurate communication in English.
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