  The current accelerated expansion of our universe could be due to an unknown
energy component (dark energy) or a modification to general relativity
(modified gravity). In the literature, it has been proposed that combining the
probes of the cosmic expansion history and growth history can distinguish
between dark energy and modified gravity. In this work, without invoking
non-trivial dark energy clustering, we show that the possible interaction
between dark energy and dark matter could make the interacting dark energy
model and the modified gravity model indistinguishable. An explicit example is
also given. Therefore, it is required to seek some complementary probes beyond
the ones of cosmic expansion history and growth history.
