  The Einstein-Hilbert action (and thus the dynamics of gravity) can be
obtained by combining the principle of equivalence, special relativity and
quantum theory in the Rindler frame and postulating that the horizon area must
be proportional to the entropy. This approach uses the local Rindler frame as a
natural extension of the local inertial frame, and leads to the interpretation
that the gravitational action represents the free energy of the spacetime
geometry. As an aside, one obtains an insight into the peculiar structure of
Einstein-Hilbert action and a natural explanation to the questions:(i) Why does
the covariant action for gravity contain second derivatives of the metric
tensor? (ii) Why is the gravitational coupling constant is positive ? Some
geometrical features of gravitational action are clarified.
