In The Education of Man, Froebel wrote, Building, aggregation is first with the child, as it is first in the development of mankind, and in crystallization. The importance of the vertical, the horizontal, and the rectangular is the first experience which the child gathers from building; then follows equilibrium and symmetry. (Froebel, 1826/1887, p. 281).
He specified that "the material for building in the beginning should consist of a number of wooden blocks whose base is always one inch square and whose length varies from one to twelve inches (Froebel, 1826/ 1887, p. 283). During the visit to the Keilhau School, Dr. Brodbeck emphasized the blocks as an important part of Froebel's teaching philosophy: "The blocks symbolized unity to Froebel as well as a belief that playing with blocks was truly an expression of the child's soul." By bringing the separate blocks together, the child expressed the symmetry of the soul and learned the meaning of unity. Froebel believed that if children could learn the unity of blocks, they also could learn the unity of the world and even unite with God, the Divine Unity. Froebel conceptualized Divine Unity in the real world, connecting spirituality with nature: .
Froebel believed that through play a child could learn to unite. He believed that early childhood, which he considered at that time to be ages 3-6, was the optimal time period for such play. .
Building on Pestalozzi's idea of "things before words," Froebel gave children early sensory experiences with blocks and other objects to generate language through play. Froebel believed that learning would occur naturally if the child held an object, observed the object from all sides, and compared it with other objects (Adelman, 2000). In The Education of Man, Froebel states that "therefore the child would know himself why he loves the thing; he would know all its properties, its innermost nature, that he may learn to understand himself in his attachment" (Froebel, 1826/ 1887, p.
