  We present a novel hybrid but thermodynamic approach to provide an
alternative to the Langevin equation by using system-intrinsic (SI) microwork
done by the Brownian particle in the kth microstate (realization). The
corresponding SI-microforce is unique to the microstate and determines the
microscopic equation of motion for it. Being a thermodynamic approach, the
equipartition theorem is always satisfied and no additional stochastic Langevin
force is needed. We determine instantaneous and long-time averages of useful
quantities and thus provide a new unified approach to the fluctuating motion
from mesoscopic to macroscopic scales.
