The belief that education of the senses is the basis of intellectual development. Didactic materials were developed to exercise children’s senses. They develop a child’s ability to differentiate qualities of color, form, size, texture, temperature, and weight. The didactic materials are characterized as self-correcting in that they only allow one correct response. The self-correcting component assures children’s inner development is being appropriately directed and allows children to work at their own pace. The didactic materials represent the primary means by which the environment is prepared, individualized, for each child.