I have been recently corrected that this sentence
"The argument can only be zero."
should be changed to
"The argument must be zero."
This is in context of a computer programme presenting an error message to the user.
For me there is not much of a difference here, apart from the second one sounding stronger (is it true?). What is native speakers view on this, please?
Best Answer
We can expand each to a perceived interpretation. Although the two are interchangeable, the second sounds stricter, with "must" sounding stronger than "can ... be". I think this is less about harshness or politeness, and more about strictness in the restriction on the argument. In my opinion, the second is clearer.
The argument, should it be given, is only permitted to take the value of zero.
There must be an argument given, and it must be zero and only zero.