How would you define "The Way" in Gathering Blue?

I would define "The Way" as tradition.  In many societies,
people's lives are governed as much by traditions and by engrained ways of doing things
as they are by actual written laws.  This is the case in Kira's society.  They are
governed by "The Way," which a harsh set of unwritten laws that reflect the way things
have "always been."

You can perhaps relate this to modern
US society by thinking about attitudes towards social welfare issues here in the US. 
Through this book, Lowry is commenting on our own attitudes in this regard.  She is
pointing out how our societal prejudices and traditions work to hurt the poor and the
disabled.  She is pointing out that we have this traditional way of looking at the
poor.  We tend to think that their problems are their own fault and so we punish them
for being poor.  This is not really caused by laws.  Instead, it is caused by our
traditional attitudes.

"The Way," then, is simply the set
of traditional attitudes that governs the way Kira's society runs.  Lowry is trying to
show us that our society is heavily influenced by our traditional attitudes and
prejudices as well.