Hence the logging time problem I've been known to agonise over.
My ATPL friends log every flight under IFR in the 'instrument flight' column. I was taught only to log time 'by sole reference to instruments'. Which is tricky.
For example, on Thursday afternoon I flew to and from the Severn bridges for a nice view in the afternoon sun. As we climbed out of our home field we passed through a thin scattered cloud layer. For a few seconds we were IMC - and we flew the entire flight under IFRs. So do I log that bit? After all, without an IMC rating it would have been illegal...
If I logged all my IFR flight time as instrument flight in the logbook I'd have a hell of a lot more - almost all my flying is IFR according to the technical definitions, with a little VFR at each end if I don't do a SID or IAP!
Tim
(edited to add - which is why it is often said that in the UK, IFR is a state of mind...)