A self-consistent scheme of random phase approximatins, for studying the properties of classical many-body systems, is defined. The case of spin ½ Ising model, with nearest neighbor interaction, is taken as the simplest representative example and the 2nd RPA is worked out in detail. The results agree with the exact high and the low temperature series expansions to the first three terms and are found to be adequate at all intermediate temperatures. These results compare favorably with those of the diagrammatic high density expansions carried to the order (1/z).