 Werndl (2009b) argues that a careful review of all systems that one commonly regards as chaotic shows that strong mixing is the crucial criterion: a system is chaotic just in case it is strong mixing. As she is careful to point out, this claim needs to be qualified: systems are rarely mixing on the entire phase space, but neither are they chaotic on the entire phase space. The crucial move is to restrict attention to those regions of phase space where the system is chaotic, and it then turns out that in these same regions the systems are also strong mixing. Hence Werndl concludes that strong mixing is the hallmark of chaos. And surprisingly this is true also of dissipative systems (i.e., systems that are not measure preserving). These systems have attractors, and they are chaotic on their attractors rather than on the entire phase space. The crucial point then is that one can define an invariant (preserved) measure on the attractor and show that the system is strongly mixing with respect to that measure. So strong mixing can define chaos in both conservative and dissipative systems.