Can someone please clear up my confusion with commas when they are used to set aside nonessential elements.
An example sentence:
After conceding defeat to his rivals, James took it upon himself to practise harder, knowing it would increase his chances of a better outcome next time.
Are the introductory adverbial and the trailing clause beginning "knowing" both using commas in the same way, to set off nonessential elements?
Therefore, a nonessential element can appear at the beginning, middle, or end of the sentence?
I've read two punctuation books--'The Penguin Guide to Punctuation' and 'Eats, Shoots, & Leaves'--and they both describe this use of the comma as 'the bracketing comma'. Both books state that these types of commas are used to set of 'interruptions', but they don't go into specifics. Are elements 'interruptors' if they can be removed and an independent clause remains afterwards (i.e., 'a sentence which still makes sense', in their words)?