AbstractFour classical theories on the stability of pool-cooled superconductors, Stekly's criterion, minimum recovery zone (MRZ), equal area theorem of Maddock et al., and Wipf's minimum propagating zone (MPZ) are reexamined and attempts to understand these theories in a unified way are introduced first.Since all of these are based on the considerations of static equilibria, they do not necessarily guarantee a stable operation in dynamic situations. So MPZ and MRZ are secondarily examined to find if they mean dynamic stabilities.