"We have been following here, briefly and roughly, a line of progressive abstraction and generalisation... the process reached... its culmination and purest expression in Joseph Louis Lagrange... Lagrange's power over symbols has, perhaps, never been paralleled either before his day or since. ...His was a time when geometry, as he himself phrased it, had become a dead language, the abstractions of analysis were being pushed to their highest pitch, and he felt that with his achievements its possibilities within certain limits were being rapidly exhausted."