Three guys walk into a bar…
ENGINEER – Is said to be a man who knows a great deal about very little and goes along knowing more and more about less and less ‘til finally he knows practically everything about nothing…
SALESMAN – On the other hand, knows very little about everything, and keeps on knowing less and less about more and more, ‘til he knows practically nothing about everything…
PURCHASING AGENT – starts out knowing practically everything about everything but ends up knowing nothing about anything – due to the years of association with engineers and salesmen.