Rebus principle

The rebus principle is the step by which a picture sign becomes a sound sign: the sign for a thing is used to write another word, or part of a word, that is pronounced alike, as a drawing of an eye can write "I". Once a script does this it is tied to one language, because the pun only works in the language whose words sound alike, and that is why a secure rebus is the standard proof that an undeciphered script records a particular language. In Mesopotamia the classic example is the sign for an arrow, Sumerian ti, used to write ti "life"; whether any such spelling exists in the Uruk IV texts is the central dispute over proto-cuneiform [@whittaker2005sumerian] [@dahl2025early]. A proposed rebus must be checked in context: the sign must not have a plausible pictorial or institutional reading, and the sound value must not be borrowed from a later period in which the sign may have changed value.