In a technical sense, ‘decipher’ means different things to different scholars. At one end of the spectrum lies Egyptian script which is more or less completely decipherable with just a little disagreement in some cases. At the other sit the scripts of Indus Valley civilization and Easter Island (Rongorongo). Between these two extremes there is a vast spectrum of opinion. We should look at the study of decipherment in terms of degrees of decipherment rather than ‘decipherable’ versus ‘undeciperhable’. Difficult-to-decipher languages fall into three categories: an unknown script written in an known language; a known script written in an unknown language; and an unknown script written in an unknown language.