  We comment on a technical critique of the free energy principle in linear
systems by Aguilera, Millidge, Tschantz, and Buckley, entitled "How Particular
is the Physics of the Free Energy Principle?" Aguilera and colleagues identify
an ambiguity in the flow of the mode of a system, and we discuss the context
for this ambiguity in earlier papers, and their proposal of a more adequate
interpretation of these equations. Following that, we discuss a
misinterpretation in their treatment of surprisal and variational free energy,
especially with respect to their gradients and their minima. In sum, we argue
that the results in the target paper are accurate and stand up to rigorous
scrutiny; we also highlight that they, nonetheless, do not undermine the FEP.
