Seeing therefore they are both [heat and pain] immediately perceived at the same time, and the fire affects you only with one simple, or uncompounded idea, it follows that this same simple idea is both the intense heat immediately perceived, and the pain; and consequently, that the intense heat immediately perceived, is nothing distinct from a particular sort of pain.

Philonous to Hylas. - Three Dialogues between Hylas and Philonous (1713)