Pace is correct, though "reasonable pilot" is subject to different perspectives. For my own experience, I must have been a "reasonable pilot" before I thought I was, because I was sent to ferry this, that and the other type with only about 600 hours total time. Just go and get it, and bring it back. No instruction. You learn to think for yourself that way as a pilot.
But it does require a level of knowledge and skill beyond "basic". I don't think that there is any formal measure. It's just one pilot seeing the skill of the other - it's really the only way. You get checked out, and checked out, until finally the check pilot just does not bother any more. Back in the day of "reporting policies" you could pretty much fly anything that the policy holder pointed you at. It seems less common now.
In the new world of insurance, I know from experience that some insurers have a heck of a time...
"Oh Mr. Pilot DAR, of your 4000 hours in single Cessnas, how many are actually in a 172?"
Pilot DAR's reply: "Does it matter?"
After a bit of convincing, it turns out that I can be insured on my buddy's 172 afterall!