The republication of Benjamin L. Whorf's articles on what Trager calls metalinguistics has aroused a new interest in this country in the problem of the relationship that a particular language may have to its speakers' cognitive processes. Does the structure of a given language affect the thoughts (or thought potential), the memory, the perception, the learning ability of those who speak that language? These questions have often been asked and many attempts have been made to answer them. The present paper is an attempt to lay bare the logical structure of this type of investigation.