It is from the Postscript. That starts with:

Postscript: Revolutions and Relativism

One consequence of the position just outlined has particularly bothered a number of my critics. They find my viewpoint relativistic, particularly as it is developed in the last section of this book. My remarks about translation highlight the reasons for the charge. The proponents of different theories are like the members of different language-culture communities. Recognising the parallelism suggests that in some sense both groups may be right. Applied to culture and its development that position is relativistic.