This year I'm on the panel of The Stage Awards for Acting Excellence at the Edinburgh Fringe. It’s meant that I’ve been able to see some stunning shows that I would have missed otherwise – most notably Thread and Mess (which, if you get the chance I urge you to catch).

In a playing field full of prizes I can see why The Stage has plumped for acting. It is an industry paper after all and the specificity means these awards have carved out a rightfully important place for themselves.

But this singular focus has made me look closely at exactly what it is that we are comparing – just what is ‘acting’? Set up to “recognise outstanding theatre performances by individuals and companies on the Edinburgh Festival Fringe,” the nominations list this year for each award is gloriously varied, but each has been chosen within a strict set of parameters.

Whilst the Best Actor and Best Actress awards speak for themselves, for the newer (and in my mind essential) categories, Best Ensemble and Best Solo Show, measuring ‘acting’ is often a harder task. Some shows which include ‘outstanding performances’ do not include any ‘acting’ and are therefore by their very nature are not eligible.

To pinpoint why this is leads us to question what ‘acting’ itself is and how we can measure it. In recent years with the rise of autobiographical and live art work, the thin line between character and self has blurred. Can you give an acting award to someone for being themselves or a version of themselves? Can you award an acting prize for astonishing physical ensemble work that favours form and structure over psychology?

I don’t think so. In such instances it has become necessary for us to distinguish between a ‘performance’ and an ‘acted’ one.

When I think of Acting (with a capital A) I think of believability, of becoming consumed and communicating a character’s story that isn’t the teller’s own. In the most basic sense – truthfully portraying someone else.

Initially I also think of the absence of ego (a la Meryl Streep) but this discounts actors such as Mark Rylance - who, while creating an utterly believable character, also appear as themselves too - which is obviously mad. Rylance extends himself to expand the people he is playing, using his own personality traits to makes theirs clearer.

I’m aware that to a certain extent this is a traditional sense of what it means to act but it is also a modern one. Laurence Olivier’s expansive performances would seem out of place now, as would Richard Burbage's who, whilst considered by contemporaries as naturalistic, also adhered to the more representational styles of the day. In a post-Stanislavski world ‘inner truth’ is the ultimate king and it’s a fiefdom that I still partially pay homage to.

How would you gauge it? As I go from show to show my own criteria are sharpening - versatility, believability, being present in the space, psychological clarity and skill are all vital for me. But some would say that these are things any performer could offer - what makes an actor an Actor for you?