1. Anybody can make mistakes.
2. We can go to the concert.
3. We could go to the concert.
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In a grammar book, it is said that 'can' in #1 is used as theoretical possiblilty' Is that right? In #3, 'could' is used as 'present possibility.' What about 'can' in #2? Which one is the surer of the two.[#2 and #3] Does #2 have more possibility or does #3 have more possibility?
Can 'can' have both 'theoretical possibility' and 'present possibility'? What is the root of the terms of 'theoretical possibility' and 'present possibility'?
#1 is said to be theoretical possibility because of the word "Anybody." No one in specific is named as the subject.
#2 is present tense and means we are able to (but don't have to) go to the concert.
#3 is more of a possibility, especially when we are trying to decide what to do for the evening!
In the context of your sentences, I can provide some explanations about the usage of "can" and "could."
1. "Anybody can make mistakes."
In this sentence, "can" is used to express a general or theoretical possibility. It indicates that it is possible for anyone to make mistakes at any time. It does not refer to a specific situation or timeframe.
2. "We can go to the concert."
In this sentence, "can" is used to express a present possibility. It means that we have the ability or permission to go to the concert at the current time. It indicates a more immediate and concrete possibility compared to the first sentence.
3. "We could go to the concert."
In this sentence, "could" is also used to express a present possibility. It implies that going to the concert is a potential option or choice, but it does not necessarily mean that it is happening or certain. It suggests a slightly less confident or definite possibility compared to sentence #2.
Regarding which one is surer or has more possibility, it depends on the context and the intention of the speaker. Generally, using "can" in sentence #2 implies a higher degree of confidence or certainty compared to using "could" in sentence #3. However, without further context, it is challenging to determine the exact level of confidence or possibility.
Both "can" and "could" can possess both theoretical and present possibilities, depending on the context and usage. The root of the terms "theoretical possibility" and "present possibility" lies in the different ways we express potential or future actions and events in language. "Can" suggests a broader and more general possibility, while "could" implies a more conditional or tentative possibility.