Taking a deep breath before leaping into reviews of the two other shows I've seen over the past week (Ranters' Holiday and Angus Cerini's Chapters from the Pandemic, coming up - I hope - tomorrow), it occurs to me that it might be interesting to some readers here if I write about the process that informs these reviews.

This blog exists for two major and extremely selfish reasons. Firstly, I adore going to the theatre, to the point that it is something like a obsessive passion: it's an artform that for me never loses the crude enchantment of innocence. Secondly, I have this compulsive desire to talk about almost everything and, in particular, an uncontrollable compulsion to talk about art.

When I first began to think critically about art, in my early 20s, the medium that offered itself as a way to begin to explore my evolving ideas was theatre. In fact, my involvement with theatre, at first as a practitioner and increasingly as a critic, has informed every aspect of my artistic practice. (My next collection of poems, due out with Salt Publishing next year, will be called Theatre: Poems). It's crucial to my creative writing to keep my critical faculties supple, and a continual engagement with a dynamic and various artform is an excellent means of keeping mentally fit.

But there's more to it than that. We all know that theatre is an impure artform, a form in which economic necessity rubs up against artistic ideals. It is impossible to pretend that theatre is not imprinted by its time and place; in other artforms, this can be less obvious, or even completely hidden. Theatre takes place in real time and in real space, and is made by real bodies. It costs money to make and to see. And yet, what crucially happens is an exchange: something is offered by the artists who make it. When I sit in a theatre and watch a show, I am the other half of that exchange. I am not a critic. I am a member of an audience.

"Exchange is creation," says the American poet Muriel Rukeyser. "In poetry, the exchange is one of energy. Human energy is exchanged, which is consciousness, the capacity to produce change in existing conditions. But the manner of exchange, the gift that is offered and received - these must be seen according to their own nature."

She is speaking of poetry, but what Rukeyser says applies equally to theatre. When I watch a show, I am receiving a gift. And no matter what it is, I do my best to receive that gift openly and without fear or prejudice, to offer in exchange the gift of my attention. I do my best, within my limitations, to perceive a show for what it is: not to expect a tragedy when I am watching the circus, not to let my own biases or expectations blind me to the gift that being offered.

Sometimes the exchange is not a happy one. Sometimes the exchange fails in the space between the auditorium and the stage. Theatre doesn't always live up to its ideals, and neither do I. But all my critique, positive or negative, stems from that experience in the theatre, during which I pay all the attention of which I am capable. My later intellectual response - the intellect is always later - is totally conditioned by what I feel in my body when I walk out of a theatre.

My qualitative responses - whether I think a piece "works" - rely on something utterly inarticulate. There are shows that I have not understood at all, or which have aesthetically or intellectually challenged every belief I have: but if I leave the theatre feeling light, excited, stimulated, alive, well then: I will have to rethink my ideas. Or, on the other hand, if I leave the theatre feeling depressed, heavy, trapped, then something is not working. The exchange is compromised; the gift is not received.

In truth, I know of nothing else to work with. "Reason," says the philosopher Gillian Rose in her beautiful book Love's Work, "is forever without ground". And the same might be said of my critique. What is most important to its formation is not at all defensible. That is just how it is: experience is incorrigible and unarguable.

Everything else - the intellectual and aesthetic framework which is articulated on this blog - is arguable. And I hope that framework is clear and informed. It's a framework that I have worked hard to create, by reading and writing and thinking, by seeing a lot of theatre over many years. But what it rests on is something any child can know and understand.

The process of critique is for me an intellectual working back, an attempt to articulate or understand why a particular work has engendered those particular effects. Sometimes it's easy to know why, sometimes it's a struggle that leads me beyond my given knowledge. But it's always a process that I find fascinating and illuminating, and that's why I keep doing it. It's really icing on the cake that other people read, and argue with, what I have to say.

This process is why I don't believe that any critique - and certainly none of mine - can ever be the last word on any work of art. It would be the height of solipsism - and even I am not that solipsistic - to think that I, alone of 50 or 200 or 800 other people in an auditorium, can have the only authentic experience in the theatre. It would also be rather dull. Any response is, rather, the beginning of another conversation. And it's all these conversations, shimmering skeins of them, over dinner tables, in newspapers and journals and blogs and pubs and cafes, that make what I understand to be a living culture. And I am very proud to be one talkative thread in the whole noisy tapestry.