"What is there in the life of each of us that requires our full attention at a particular age, that is vital for that age or for coming ages and cannot be postponed?" This is the question Caleb Gattegno poses in his age-specific trilogy The Universe of Babies, Of Boys and Girls, and The Adolescent and His Will. This original monograph provides an entirely new set of tools for the study of early childhood, and offers powerful insights into the relationship of man to himself. The constant use of consciousness as an instrument of study sheds light on how children learn what they must learn and yields a broader understanding of human functionings.