If you're an acupuncturist there doesn't really get a more basic question than 'What is Qi?'. I mean: it's the equivalent of asking a sailor what water is, or a farmer what soil is...
Worryingly I've asked this question to a few acupuncturists in the past and not got much back, and it was partly the inspiration to write my book. Some acupuncturists even replied that it was undefinable, indescribable... Imagine a farmer saying that soil was indescribable?! It would be fair to conclude that the farmer probably didn't know what he was doing.
It really concerns me that the acupuncture community still hasn't got this one nailed down, and thankfully I think it's fairly simple. To be coherent the Qi of the universe also needs to describe what I would call medical Qi: the Qi that moves strongly in our bodies.
Universal Qi can be seen as the way in which matter is made manifest, in other words the organisational energy of the universe. The cosmos started as a huge fireball (perhaps) but as it cooled patterns started emerging. Science describes these patterns as the myriad forces and laws of nature... however, science is obsessed with the idea that all these forces boil down to a single law - what is calls the Theory of Everything (TOE). Qi is that single force.
In the body, when a single cell creates the 100 trillion cellular team that our bodies become, matter is becoming manifest too. The force that controls this is also Qi and is highly concentrated because we are alive. Hence my definition of Qi would be:
That's why you can see it in action here: