. Excluded possibilities in science
have a funny way of reentering the picture years later in radically different
dress, although this is a lesson that scientists have been slow to learn.

<P><A NAME="showpaths"></A><B><FONT SIZE=+1>Show Paths To Goals</FONT></B>

<P>It is possible to know, or even to prove, that a goal is attainable
while at the same time remaining ignorant of how to actually achieve it.
Even if all of the necessary resources and methods are at one's disposal,
a critical sequence of steps 