Again, yes we could find the match on "Brown", but if you have many people with a last name of "Brown" and differing first names, the likelihood of getting the match "right" goes way down. In general, if you can think of a way to tell a human being how to find a match, then we can translate it into computer language. But if your human method isn't 100% reliable, the computer version won't be any better.
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.