  Argument systems are based on the idea that one can construct arguments for
propositions; i.e., structured reasons justifying the belief in a proposition.
Using defeasible rules, arguments need not be valid in all circumstances,
therefore, it might be possible to construct an argument for a proposition as
well as its negation. When arguments support conflicting propositions, one of
the arguments must be defeated, which raises the question of \emph{which
(sub-)arguments can be subject to defeat}?
  In legal argumentation, meta-rules determine the valid arguments by
considering the last defeasible rule of each argument involved in a conflict.
Since it is easier to evaluate arguments using their last rules, \emph{can a
conflict be resolved by considering only the last defeasible rules of the
arguments involved}?
  We propose a new argument system where, instead of deriving a defeat relation
between arguments, \emph{undercutting-arguments} for the defeat of defeasible
rules are constructed. This system allows us, (\textit{i}) to resolve conflicts
(a generalization of rebutting arguments) using only the last rules of the
arguments for inconsistencies, (\textit{ii}) to determine a set of valid
(undefeated) arguments in linear time using an algorithm based on a JTMS,
(\textit{iii}) to establish a relation with Default Logic, and (\textit{iv}) to
prove closure properties such as \emph{cumulativity}. We also propose an
extension of the argument system that enables \emph{reasoning by cases}.
