Few men of genius are keen; but almost every man of genius is subtle. If
you ask me the difference between keenness and subtlety, I answer that it
is the difference between a point and an edge. To split a hair is no proof
of subtlety; for subtlety acts in distinguishing differences--in showing
that two things apparently one are in fact two; whereas, to split a hair is
to cause division, and not to ascertain difference.
_October_ 27. 1831.