The well-known linear relationship (T-DELTA-S# = alpha-DELTA-H# + beta, where 1 > alpha > 0, beta > 0) between the entropy (DELTA-S#) and the enthalpy (DELTA-H#) of activation for reactions in polar liquids is investigated by using a molecular theory. An explicit derivation of this linear relation from first principles is presented for an outersphere charge transfer reaction. The derivation offers microscopic interpretation for the quantities-alpha and beta. It has also been possible to make connection with and justify the arguments of Bell put forward many years ago.