Truth and Method/II.2.1Biv The principle of history of effect (Wirkungsgeschichte)
In this section, Gadamer deals with the idea of horizon of understanding. This is something he is well known for and many will learn this much and no more of his ideas: that an interview is a fusion of two people's horizons of understanding. A nice idea, but no-where to be found in Truth and Method. In fact this represents a trivialisation or domestication of the real point he was trying to make. Gadamer is talking about understanding as a historically effected event.
He says on page 311,