Because when speaker uses some certain tone to highlight a certain aspect of the text in order to better illustrate how he feels about a certain subject. In order to display two sides of everything in the text to further build the core point, the speaker compares two separate items into a compound word.
When it comes to life and nature, Jack London and Robert Frost have different perspectives various things that they agree upon but others that they do not.
Which source provides the most reliable information? a personal blog an article published in a scholarly journal a classmate's Twitter post a wiki article written yesterday