The Daniel Jones Cardinal Vowel system, defined as it is by clear-cut and rigid rules, is part of the stock-in-trade of all IPA phoneticians. I wish to suggest that the present format of the system contains a contradiction so basic that any attempt to make use of it as a descriptive technique, in all but a very restricted number of cases, would be completely impossible. This contradiction, moreover, is so obvious that the fact that no phonetician has called attention to it until now is hard to explain, and the equally certain fact that descriptive phoneticians (including the present writer) regularly teach the use of the technique to students, and apply it themselves, is even more so.