My colleague, Philip Fisher, wrote a piece addressing the above question. What follows should be viewed as a supplement to Philip’s article (which I heartily commend to you).

As a critic, it is my duty to all parties to give my honest, informed opinion on any performance I review. My use of the word ‘duty’ here is neither incidental nor pompous: a great deal of human endeavour has often gone into mounting a production (and let us not forget the hard work many audience members put into earning the cash that enables their attendance).

As a critic who also (occasionally) writes creatively for the theatre, I aim to tell the truth but to do so constructively. It’s part of the critic’s job to say not just what we think but also why we think it.

I confess, in my early days, I was sometimes unnecessarily harsh—the truth, I have since learned, rarely needs to be brutal.

If exceptions to this general rule can be found in some of my reviews, careful examination will show a correlation between the tenor of the critique and the charge for attending that production. It irks me whenever I feel the public are being taken for a ride, and I will continue to do all I can to dissuade people from wasting money and those few precious hours of their lives on such shakedowns.

I try to write well—i.e. clearly and entertainingly—but to resist being a ‘smart Alec’ just for the sake of it. Even Dorothy Parker’s fabulous put down of Katherine Hepburn’s acting (she “ran the gamut of emotions from A to B”) is allowable only as an honest assessment. Of course, others adored Hepburn. Which brings us to matters of opinion, taste and truth.

A companion and I were discussing a show we’d just seen, when a third party, who had attended the same performance, joined us and asked what we’d made of it. My companion lamented:

“I thought I’d enjoyed it, until Martin explained to me why I hadn’t.”

Theatre criticism is not mathematics or physics. There are few hard facts (although if a Macbeth asks, “Is this Mick Jagger which I see before me?”, it’s safe to say he’s messed up). Nevertheless, a competent theatre critic will understand the established and broadly accepted criteria by which we may judge a piece of theatre to be good or bad. Indeed, to claim that something is a good (or bad) instance of something, already implies there is more than personal taste involved.

You may like or dislike crème brûlée—that’s entirely personal. Either way, it makes sense to talk about good and bad crème brûlées, simply because there are broadly accepted ingredients and methods of preparation. It’s the same with theatre.

Regarding the performance we’d both just witnessed, my companion was entitled to like what he’d seen, notwithstanding my detailed explanation of where and how it fell short of being good theatre.

One of the reasons I continue to read the reviews of other critics is that that there are still plenty out there who know more than I do. By and large, a critic should have more knowledge about theatre (through education, experience and reflection) than the average punter.

There are, however, legitimate exceptions. I had no knowledge of the South Asian classical dance form, Bharatanatyam, when I attended a performance by Seeta Patel (now regularly to be seen mentoring contestants for the BBC’s annual Young Dancer competition). In this case, my review aimed at communicating my enchantment. I felt this performer (and her art form) should reach a wider audience. I didn’t know what was good, but I knew what I liked—how the music and the dancing had made me feel—and I was keen for others to experience that.

I was sharing my joy, and this is one more role for the critic. When Aristotle observed that human beings are political animals, he meant we need a community (a polis) in order to thrive (we’re not solitary creatures like some other species). We like to have company. We crave mutuality.

This is why many of us read what critics write about shows we’ve already seen, or about last night’s TV. “What did she think of what we watched? How clever (and right) she is!” (Alternatively, “What an idiot! How does she make a living doing this?”).

Finally, again as Aristotle noted, while 2 + 2 will forever equal 4, criteria for judgement in human endeavours are not eternally fixed. The critic can (very occasionally) recognise and promote the work of an artist who challenges and resets the boundaries. Kenneth Tynan, it is said, did such when he championed John Osborne’s Look Back in Anger.

Despite George Bernard Shaw’s claim that a critic is one who “leaves no turn unstoned,” most of us love theatre like a tiger mother: because we love you, Theatre, we will push you to be the best you can be. Properly done, it’s a service to those who produce the art form, as well as those who consume it.