is accent emphasis?

This was a tricky one. A master’s student from Chile wrote

I'm currently working on the theoretical framework for my final research work which is entitled "The glottal stop and its emphatic function in word-initial prevocalic position." At the moment, my attention is focused on endeavouring to validate this emphatic function.

For this purpose, I've been trying to observe other phonetic, phonological, syntactic and semantic features that have been proved to have an emphatic function; one of them most certainly has to do with intonation. I've been reading your book on English Intonation, which I must say is a must, and there's a point in the introduction I would like to ask you about: on page 7 you write, when referring to tonicity, that "speakers use intonation to highlight some words as important for the meaning they wish to convey. These are the words on which the speaker focuses the hearer's attention. To highlight an important word we accent it." One conclusion I think we may draw from this is that accented words then may be considered as "emphasis-carriers".

Later on the same page, you write that the most important accent in the IP is the nucleus. This would mean, as far as I understand, that the word which contains the nucleus is a word that carries more emphasis than the other accented words.

Even later on that page you write that the nucleus "indicates the end of the focused part of the material." Do you consider it would be correct to conclude then that emphasis is carried by the portion of the intonational phrase that goes from the first ("regularly") accented syllable to the nucleus? Which part of that portion would you consider to carry the greatest degree of emphasis? Although I believe I have an answer to that question (the syllable that contains the nucleus of course, and, to a lesser degree, the other accented syllables) it would be really important for me to have your most valuable opinion on this matter.

I’m afraid it took me a little time to reply. Here’s what I eventually said.

As I understand it, 'emphasis' is a pragmatic concept. Its relationship to prosodic features is complex. Perhaps the most difficult point is: do you agree with me that many utterances are wholly unemphatic?

Impressionistically, I would expect that emphasis might typically involve deviating from the unemphatic norm by, for example, one or more of the following:
1. widening the pitch range on the nucleus
2. using a higher pitch range throughout
3. increasing the volume (loudness)
4. using a high prehead rather than the unmarked (low) prehead
5. reinforcing initial vowels by a glottal stop ('hard attack')
etc.

From what I write in the book English Intonation you want to conclude that "accented words may be considered as emphasis-carriers" and "the word which contains the nucleus is a word that carries more emphasis than the other accented words". I disagree, though obviously it depends on how you define emphasis. If you agree with me that many utterances are unemphatic (have no emphasis), then it is wrong. If you believe that all utterances include some degree of emphasis, then I suppose it is arguably true. But you would merely be relabelling accent as emphasis.

You must take my words in English Intonation at their face value. [...] All of what I say there applies basically to what I consider to be unemphatic speech. Every IP requires that certain syllables be accented, independently of whether anything is emphasized. For me, accentuation is not the same thing as emphasis.

I hope this is helpful.