What an investor needs is the ability to correctly evaluate selected businesses. Note that word “selected”: You don't have to be an expert on every company, or even many. You only have to be able to evaluate companies within your circle of competence. The size of that circle is not very important; knowing its boundaries, however, is vital.
Therefore we pledge to bind
ourselves to one another, to embrace
our lowliest, to keep company with
our loneliest, to educate our illiterate,
to feed our starving, to clothe our
ragged, to do all good things,
knowing that we are more than
keepers of our brothers and sisters.
We are our brothers and sisters
Women observe subconsciously a thousand little details, without knowing they are doing so. Their subconscious mind adds these little things together - and they call the result intuition.
If we were to lose our fish that we appreciate so much by overfishing; or if we were to lose some of our favorite beaches to overbuilding and pollution, then how would we feel? It's become a case of not knowing what you've got until it's gone.
The physician himself, if sick, actually calls in another physician, knowing that he cannot reason correctly if required to judge his own condition while suffering.