CLOS question: method combination

[Kerry Kimbrough <Kimbrough@dsg.csc.ti.com>]

True or false?

  The CLOS specification allows an auxilliary method (e.g.  :after, etc.) to be
  defined on a generic function for a particular set of specialized args, *even
  though* there is no primary method defined for these arg types.

The spec says that method combination will signal an error in this case, so the
question really has to do with when method combination can occur. If the answer
to the question is "True", then I am free to define a "mixin" which qualifies a
primary method supplied by some other class (which I know will be there when I
instantiate). If "False", then I can't do this (ouch!).