Changing to models that allow for new goods requires a subtle but
important shift in the unexamined assumptions and habits of thought that
we bring to any problem. By their very nature, these habits and assumptions
are things that we take for granted, so it takes an effort to bring them to the
surface and subject them to analysis. To do this, it helps to go back prior to
the introduction of formal equilibrium theory and retrace some of the logical
steps that led to the unification between dynamic analysis and static analysis
that mainstream economists now take as obvious.