 The considerable gap between the two stages of Grimm's development of these editions is shown by the fact that the second volume addresses phonology in 600 pages – more than half the volume.Grimm had concluded that all philology must be based on rigorous adherence to the laws of sound change, and he subsequently never deviated from this principle.This gave to all his investigations a consistency and force of conviction that had been lacking in the study of philology before his day.