This is the title of a paragraph in the book "Chinese: A Comprehensive Grammar", by Yip Po-Ching and Don Rimmington, whose content I find really hard to understand. The explanation:
是 shì may also be used loosely to refer to or to make an overall assessment of a situation, rather like its function as a marker of emphasis.
And then some examples:
I don't think she will come./She is unlikely to come.
So far we have tried whatever methods we could think of.
I cannot understand what the explanation is supposed to mean. The paragraph before this one explains how to use the "是…的" construction to emphasize, so I also cannot understand the difference between these two patterns, and if the omission of 是 in the example sentences changes the meaning.