In its widest sense, this term denotes the central section of a historical process taking place in three or more stages, whether this process is regarded as a progress, a decline, or a cycle. The concept of a “middle” epoch was implicitly known to Christian historical tradition, since the triple division of the Apostle Paul (ante legem, sub lege, sub gratia) , which influenced later attempts to divide sacred history into periods (Joachim of Fiore: age of the Father, of the Son, of the Holy Spirit). Th…