  Normal mode decomposition of atomic vibrations has been used to provide
microscopic under-standing of thermal transport in amorphous solids for
decades. In normal mode methods, it is naturally assumed that atoms vibrate
around their equilibrium positions and that individual normal modes are the
fundamental vibrational excitations transporting heat. With the abundance of
predictions from normal mode methods and experimental measurements now
available, we care-fully analyze these calculations in amorphous silicon, a
model amorphous solid. We find a number of discrepancies, suggesting that
treating individual normal modes as fundamental heat carriers may not be
accurate in amorphous solids. Further, our classical and ab-initio molecular
dynamics simulations of amorphous silicon demonstrate a large degree of atomic
diffusion, especially at high temperatures, leading to the conclusion that
thermal transport in amorphous solids could be better described starting from
the perspective of liquid dynamics rather than from crystalline solids
