For reasons which now are mysterious to me, but which probably reside in a diabolical subconscious masochism, I decided to see three Adelaide Fringe shows yesterday, which also happened to be the day I arrived. I found myself scrambling from show to show, with barely time to draw breath between each one. It's not an ideal way to see theatre, at least not for me: I like to think about what I've seen before being flooded with yet more stimuli. But as a crash course in the theatrical variety on offer at the Adelaide Fringe, it was probably exemplary.

The first was a rather charming piece of audio-instructed theatre, En Route, by Melbourne group Bettybooke. This won the Best Live Art Award in last year's Melbourne Fringe, and is, as they say, a "pedestrian-based event", in which mobile phones, iPods, hidden letters, chalked signs and company members lead you on a kind of Easter Egg hunt through the Adelaide CBD, with the city itself as the prize. It's part of an international trend of headphone-centric theatre that seeks to put the audience in the middle of the performance: through its insistence that participants look out, as it were, through their skull, it generates a crowded solitude that is at the centre of urban experience. The stage is the city, the theatre is your imagination, and the presiding god is Ranier Maria Rilke, whose insistence on the gaze is one of its final meditations.

There are 17 tracks, each accompanying a different route, and each offering a different audio experience that features music by local Adelaide musicians. Some are simple instructions ("walk slowly, take your time, look..."); some are narratives, such as a saunter through a bizarrely empty shopping arcade to a detective story; some are meditations on the act of perception by people like Maurice Merleau Ponty; others generate a mood for a walk down a particular lane, or create a background to a short exhibition of artworks about Dante's Purgatorio, shown in a carpark stairwell. It's a complex show, because the perspectives are constantly changing, but it's fun because it's constantly surprising, and it generates a nice balance between the participant's freedom and its own structuring necessities. I thought it a little long - maybe the ideal length for a show of this sort is an hour - but it kept me constantly interested while, of course, giving me some healthful exercise.

In an illustration of the perils of making theatre in an uncontrolled environment, my En Route began with a couple of security guards taking violent exception to Bettybooke "conducting its business" on the verandah of the Adelaide GPO, backed by a chorus of outraged staff members. I can't imagine what they thought we were doing, as they warned me against the sinister man ("don't trust him!") who was fitting me up with an iPod; perhaps they thought we were dealing drugs. Who knows? Their hostility was in marked contrast to this show's essential innocence, which was maybe what I liked most about it.

After that, I had time for a G&T in the diverting environs of the Garden of Unearthly Delights before heading to The Hive - a tent with chairs - for Baba Brinkman's The Rap Guide to Evolution. Brinkman is a Vancouver rapper whose last work was, apparently, a rap version of Chaucer's Canterbury Tales. After a performance of that show, he was approached by a scientist who asked him if he could do the same for Darwin as he did for Chaucer, and thus was produced what Brinkman calls "the very first peer-reviewed hiphop show".

Anyone who thinks rap is just about gangstas and hos should take a look at this (as it is as instructive about the social origins of rap as it is about Darwin, it might equally have been named The Evolutionary Guide to Rap). After a fair bit of forceful campaigning from my kids, I've had to lower my prejudices: rap is the popular poetic form, it's as various as any art, and there's some classy stuff in there. This is probably one of its stranger manifestations, but Brinkman's Byronic wit and performative energy combine to make it an irresistible hour. Plus you get to learn a lot about mitochondria and the social behaviour of slime moulds. Wearing a t-shirt with a picture of Darwin (and the slogan "Very Gradual Change You Can Believe In"), Brinkman takes us through 10 chapters, in which he explores various aspects of Darwin's theory (and attacks the whole premise of Intelligent Design), ultimately to reveal the humanity and "grandeur" of Darwin's vision. Science is seldom this much fun.

My final destination was a performance of My Name is Rachel Corrie, at X Space at AC Arts. Edited from the writings of young activist Rachel Corrie by Alan Rickman and Katherine Viner, it premiered at the Royal Court in London before running into controversy when the New York Theatre Workshop "indefinitely postponed" its performance in New York in 2006. Although I followed the various controversies with interest - this is a play that situates itself right on top of the Israel/Palestine political faultline, and generates as much seismic activity as one might expect - I haven't before now had a chance to see it.

As is well known, Rachel Corrie was killed in Gaza in 2003, when she was crushed by a bulldozer while defending a Palestinian home from being demolished. At the time, she was part of a band of non-violent international activists who sought to protect the homes, properties and lives of the Palestinians by interpolating their bodies between them and the IDF, on the assumption that killing a foreign national would cause more trouble than a Palestinian. The play is taken from her emails and diary entries, and follows the trajectory of a bright, idealistic young woman with enormous personal courage. It is also - and this is where the controversy stepped in - a bald statement about the daily persecution of ordinary Palestinians in the Occupied Territories.

In this rather beautiful production directed by Daniel Clarke, Hannah Norris gives a passionate and accurately observed performance of Corrie. As the play opens, she stands amid a pile of cardboard boxes in the mess of her chaotic bedroom. The first half consists of recollections from Corrie's school and college years, and her early activism. This, the most engaging part of the play, is staged with effective simplicity, with Norris bit by bit packing away her belongings as she speaks. She's funny, innocent, smart, ironically aware of the pitfalls of being a "progressive", and remarkably intelligent. In the second half, when Corrie journeys to Palestine, the boxes become the walls and houses of Palestine: some open up to reveal miniatures of houses, or spill out a rubble of children's shoes and stones. This section's staging was much fussier, with actions that seemed merely decorative - the arranging of the children's shoes in the shape of a heart, for instance.

The production's conscious theatricality heightened the problem with using this kind of verbatim script: criticising it is a little like attacking a memorial service for using bad grammar. Here the play is presented as theatre, but it carries with it a weight of authenticity that closes down responses. It's like being in church: its polemic is unforgiving and earnest, with the constant reminder that behind this theatrical illusion is a dead woman. One is supposed to be moved, or one is heartlessly dismissing this awful death.

I wasn't moved, but it wasn't because Norris's remarkable performance lacked any skill or feeling: it was the set-up of the whole play, which left me no room to respond, either emotionally or politically. What if you already know about the IDF demolitions of houses, gardens and olive groves, or the daily harassment of civilians in the Occupied Territories? Is your task in this theatre, then, simply to nod in agreement (or, alternatively, to rage in disagreement?) And does either response really lead to thought?

I prefer, for example, Brecht's approach, which understood the power of Verfremdungseffekt, the "making-strange" which permits - rather, which insists on - active thinking as a response, in order to get beyond the singular focus of empathy (which Brecht thought fatally bourgeois). There's a Zizekian argument to be unpacked here, which I have neither the time nor the energy to follow through: but Howard Barker says it all quite well from the aesthetic side of the equation. Uncomplicated empathy is what drives this show; it's a well-realised production done in complete good faith, but it demonstrates that empathy is not enough for either political or artistic radicalism. Which is not at all the same as saying that it ought not to be there.

En Route, concept by Julian Rickert, created by Bettybooke - Suzanne Kersten, Claire Korobacz, Paul Moir and Julian Rickert. Adelaide Fringe, until March 14.

The Rap Guide to Evolution, Baba Brinkman and SPL Productions. The Hive, The Garden of Unearthly Delights, Adelaide Fringe, until March 13.

My Name is Rachel Corrie, from writings by Rachel Corrie, edited by Alan Rickman and Katharine Viner, directed by Daniel Clarke. Design by Cassandra Backler, lighting and sound design by Ben Flett, video by Annemarie Kohn. Performed by Hannah Norris. X Space at AC Arts, Adelaide Fringe, until March 14.