Because of our carefully guarded knowledge in our own area, and the resultant status afforded us by society, we are also presumed to be wise in other areas, legal, financial, geological etc. And, of course, mechanical.
Last week, I came upon Joe broken down by the side of the road (his car was broken down, I mean).
As there was nothing good on TV and I felt that after a tough morning surgery, I deserved some free entertainment (did I mention it was raining heavily?), I stopped to have a closer look.
The mandatory crowd had gathered to offer unwanted advice, but when Joe saw my arrival, his face lit up.
'Doctor,' he said, 'what do you think?'
Now, I know as much about car engines as I do about interpreting electrolyte lab results, but I haven't got where I am today by being unable to cover up that I haven't got a clue what I'm talking about.
So I had a stock phrase ready and prepared for this very situation, partly inspired by the Father Ted episode where Fr Jack is conditioned to respond to every question with: 'That would be an ecumenical matter.'
I kicked the tyres (because some conventions must be observed), then leaned over the engine, paused for a theatrical moment, scowled as if disgusted by what I was looking at, and then asked: 'Did you try the carburettor?'
A satisfied murmur went through the crowd and Joe said: 'I hadn't thought of that.'
Gratified by the reaction, I allowed myself an encore.
'Could be water in the carburettor,' I opined solemnly. The bucketing rain grew even heavier, adding gravity to my words, none of which, you will note, were directive, but had been couched in general terms, giving me an escape clause and absolving me of any responsibility for the outcome.
'Of course, I'd need to look underneath,' looking around yearningly as if my dearest wish was for a water-proof tarpaulin so I could crawl under the engine, while simultaneously triggering my phone to ring and pretending to answer it.
'Rats, an emergency, gotta go right now,' I said, squelching away quickly. 'My work here is done.'