We summarize some of our recent measurements of the temperature dependence of the optic index of refraction, n(T), in several different classes of ferroelectrics. The common thread between these different materials is that in all of them the translational symmetry is strongly broken. Far above the usual ferroelectric transition temperature T, up to a temperature T,, we show that the crystals possess a local, randomly oriented, nonreversible polarization. Using a simple model for this behavior, we can account for it qualitatively and in some systems quantitively understand T,. We believe this model contains the basic physical understanding of ferroelectrics that have a diffusive phase transition. © 1986, Taylor & Francis Group, LLC. All rights reserved.