This paper presents attempt to explain the phenomenon of the stability loss of prismatic columns, made of metal, loaded beyond the yield limit. The explanation is presented on the base of Euler’s theory, tangent modulus theory, reduced modulus theory, Shanley’s column paradox and inelastic column theory. Explanation refers to results of experiments performed by many scientists, including F. R. Shanley, and related to Huber-Mises-Hencky (HMH) hypothesis of material effort. The use of HMH material effort hypothesis to analyse buckling column within inelastic range enables to explain the mechanism of buckling (including strain development) observed by F. R. Shanley and points out that the column paradox does not exist. The change of the uniform state of strain and stress to the non-uniform state which does not lead to loss of total stability by column is referred to as the loss of internal stability. The concept is presented on the base of idealised stress-strain diagram (bilinear elasto-plastic model).