Terms denoting political attitudes, such as ‘conservative,’ ‘liberal,’ ‘radical,’ and ‘reactionary,’ have long been familiar both in popular usage and in the language of political science. Though sufficiently understood for ordinary discourse, their use is likely to lead to a confusion between a political opinion and the type of person who holds the opinion. There is considerable agreement as to what is meant by a radical view; but is there such a thing as a radical type of personality? If there is, we need a method for the measurement and identification of such individuals. If not (and psychologists are becoming increasingly suspicious of type classifications), we must ask what psychological characteristics in individuals are the most likely to produce a radical trend in political and social convictions. The same observation holds for the other familiar attitudes upon public questions. A logical procedure would seem to be, first, to measure the distribution of public opinion in a representative sample, and secondly, to select from the various regions of this distribution (conservative, radical, and the like) a sufficient number of individuals for detailed study of the motives and traits of their personalities which give rise to the opinions they hold. This paper will be devoted to a preliminary report on the results of such a study.