rationality, the existence of the *defeated* argument $c$ should not change the preferences ${\cal A}_1$ has already established given the arguments $\{a, b\}$. Indeed, such a change of preferences can be problematic in practice. For example, when an intelligent system needs to determine a set of actions, choosing $\{ a \}$ given $\{a, b\}$, while choosing $\{ \}$ given $\{a, b, c\}$ does typically not make sense, *ceteris paribus*. Figure \[fig:examples\] depicts the argumentation graphs of $AF$ and $AF'$.

To address the problem of *reference dependence* in abstract argumentation, this paper provides the following contributions:

1.  Firstly, it characterizes the concept of reference independence in the context of argumentation semantics and argumentation framework expansions.

2.  Secondly, it proofs that well-established argumentation semantics cannot guarantee reference independence for normal argumentation framework expansions.

3.  Thirdly, it proofs that argumentation that is based on normal, non-cyclic expansions–which we refer to as *rational man’s expansions*– guarantees reference independence.

4.  Finally, it puts *reference independence* and *rational man’s expansions* in the context of preference-based argumentation, an argumentation approach that explicitly models agent preferences. This shows that reference dependence is also a problem for preference-based argumentation, which can, however, in this case not be solved with 