Professional Public Speaking skills

What are professional Public Speaking skills? 
If professional means earning a living or part of a living by doing something, then presumably you could make a case for claiming to be a professional if someone happens to offer you £10 for speaking on an occasion, or maybe even if you are asked to speak in exchange for a crate of beer. 
Equally there are many experts who are paid significantly to share their knowledge, even though their presentation skills are lacking. 
We live in a time when some politicians insist that they are honest because through some legal technicality it cannot be proven that they are dishonest. 
So just highlighting some specific element of what might define a professional and making a claim that that in itself is proof of excellence can be quite a leap of logic.
There are many inviations in the public speaking training sector offering to teach you to be a TED speaker, or how to monetise your speaking.  I remember visiting a speaking organisation and the whole event seemed to be about how to make money or more money from speaking.  I have no specific objection to that.  What disconcerted me a little was that there seemed to be very little mention of actually being any good at speaking!

Therefore to slightly adapt ‘Exhibit A’, which is often offered in many classes on logic
                All men have two legs
                Socrates is a man
                Therefore Socrates has two legs
is not the same as
                All men have two legs
                Socrates has two legs
                Therefore Socrates is a man
(because of course there are many other creatures that have two legs)
So although they sound quite similar, they are not the same.

I find there is a similar sleight of hand in when it is suggested
                Many TED speakers are great speakers
                John is doing a TED talk
                Therefore John is a great speaker

Instinctively we know something is not quite right in the logic of the last statement.  (And if you want to look precisely into why an apparent statement of logic does or does not hold, look up ‘syllogism’ on the internet and find out about ‘major terms, minor terms and middle terms’ and how whether they are or whether they are not ‘distributed’ can lead to a statement that is definitively true or one that just sounds as if it is! 
And then if that sounds like fun and you still have a few moments, take a look at many current TV adverts and analyse for instance how although you would love to be irresistible to other human beings, and how even though the main character in the advert clearly is irresistible - apparently because of a certain scent he is wearing - it does not automatically follow that if you buy the same scent, that you too will be irresistible.

All of which brings us back to professional Public Speaking skills.
And please note, I am talking about professional Public Speaking skills, not necessarily being a professional public speaker – however we choose to define that.
Coming from a musical background, as impressive as a CV might be, where a person had studied and where they had performed, in the end the simplest way to establish credentials was simply to say:
‘Play something!’
If it walks like a duck, swims like a duck and quacks like a duck, it is probably a duck.
Or according to Matthew in the bible:
‘Ye shall know them by their fruits’

In the end, most of us can identify a good speaker.  We don’t necessarily need to be able to analyse why.

When I was briefing a judging team for a speech competition, I would tell them there are two ways you can approach this.
There will be a succession of excellent speakers, so you are unlikely to be choosing between ‘good’ and ‘bad’.
Therefore it might be quite hard to decide who the best, but you might realise that there are some you ‘like’ better than others.
So the first approach is to use the very detailed assessment card we are giving you, with marks to be given for voice, stance, gestures, structure, vocabulary, et al.  Then you add up all your marks and the one who has the highest total is the winner.  This approach works very well in a running race; the person who runs 100 meters the quickest is the best.  Speaking contests, music contests and for that matter cooking contests are always going to be a little more subjective.
The second approach is maybe to write down a couple of notes to remind you who was who, and to simply, judge based on who impressed and who stayed in your memory most.
In reality you would probably want to do a blend of both approaches. 
If one speaker did not score too well, but made a great impression on you, you might want to work out why that was the case and either go with your feelings because the overall impression vastly outweighs the technical scores, or else you may realise you have been over-influenced by some personal preference that cannot be justified by the overall performance.
The point is simply that sometimes the sum of the parts can be a lot more or a lot less than the overriding impression.
I remember at school when I took my Grade 8 cello exam, I could see the examiner writing his marks down as I delivered the various sections of the exam.  I was able to tot up and realised that I might have just scraped a distinction, for which I was quite pleased.
When I got the official result through the post the overall mark was quite a bit higher than the sum of the scores I had seen him jotting down.  Presumably at the end he had taken an overall impression of the exam, decided that it was a bit better than the marks he had written down for each section, and so went back and added a couple of marks here and there to justify his final total.

Assessing speakers will be even more subjective.
If I play a piece by Beethoven, Beethoven may not be the listener’s favourite composer, but I am sure they would no major objection to Beethoven, however if I speak about legalising cannabis, allowing more refugees into a country, raising taxes, banning a demonstration, how the audience feels about the content of my speech will have an enormous influence on how persuasive or credible I seem.
I have witnessed judges making – in my terms – quite remarkable decisions based on what they chose to prioritise.

On a public speaking score sheet, I am not sure how well Greta Thunberg would do in a competition, but that in reality is only a small part of what she is judged on.  More important are her words, her examples and most important of all, the resonance of her message.
So in the end, if we think about walking, swimming, quacking ducks, what are professional public speaking skills?  On a day to day basis, at work, or on any regular platform, delivery, structure, style and content all matter, but sometimes what matter most is simply to have a purpose and a passion.
When they are in place, often all the other skills follow on automatically, or if they do not do so completely, somehow it does not seem to matter that much!
That is what enables a mother at a school meeting or a local resident at a council meeting speak with a power and conviction that cannot be countered by the cool competence of a paid expert.

Maybe we should not be using the word ‘professional’ at all
All that matters is belief and passion.