This book contributes to the current debate about how to think and talk about human thinking so as to resolve or bypass such time-honored quandaries as the controversy of nature vs. nurture, the body and mind problem, the question of learning transfer, and the conundrum of human consciousness. The author responds to the challenge by introducing her own "commognitive" conceptualization of human thinking. She argues for this special approach with the help of examples of mathematical thinking. Except for its contribution to theorizing on human development, the book is relevant to researchers looking for methodological innovations, and to mathematics educators seeking pedagogical insights and improvements.