And then Heisenberg came to see me; or did he? It was disconcerting; by the time the light had travelled from him to me and I could see where he was, he had changed position. This made eye contact difficult and counselling even more useless than usual; he was moving too quickly to allow me to pat him on the knee and say: 'There, there.'
His history was fittingly ambiguous.
'How often do you get the pain?' I asked.
'Now and then,' he replied.
'Where is the pain?'
'Here and there.'
'What do you work at?' I asked, by this stage pretty sure of the answer I'd get.
'This and that,' he dead-panned.
The Uncertainty Principle can be a bit of a Bohr, but in general practice, uncertainty is not an ignoble state; managing uncertainty is one of its great challenges. We are compelled to make the marginal call every day, based on experience and intuition; as WB Yeats said: 'We are closed in, and the key turned/On our uncertainty'.
We know that every kid with a URTI can turn out to be meningitis a few hours later; every minor chest pain or indigestion can suffer an infarct after walking out the door, marshalled by our reassurance; and that an obvious case of gastroenteritis can become a florid acute appendicitis.
But we can't play safe all the time. We can't admit them all to hospital for observation - the system would come crashing down in flames. We are the thin red line, protecting our hospitals from the barbarians at the gate. Referring is easy; deciding not to refer is the hard decision, a decision we know can end in tragedy.
We can't pass the buck, we have to make the call, and when we get it wrong, as will inevitably happen, we will get the blame.
Certainly, there's no uncertainty about that.
- Dr Farrell is a GP from County Armagh. Follow him on Twitter @drlfarrell.