In an age of scientific method much of any individual's thinking is quantitative. He lives in a world in which every situation involves concepts of quantity, amount, size, or number. He employs number language, that is, number names and signs to express his quantitative ideas. These various number names and signs constitute the medium for his number thinking. But, the individual is not able to use number concepts in his quantitative thinking until he develops the ability to express them in appropriate verbal form. This implies that an understanding of number concepts and processes is necessary to an understanding of the interrelationships among his number ideas. Hence, the quality of an individual's quantitative thinking is conditioned by his ability to deal with quantitative language. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]