The first three planes of development (0 - 6, 6 - 12, 12 - 18) address age ranges that, by most contemporary definitions, fit neatly within our concept of "childhood." But what about someone in the fourth plan (18 - 24)? 

Before answering, consider this. Contemporary Americans would balk at the idea of a 11 year old in the workforce, yet in 1900 18% of the U.S. labor force was under 16. Today, billions are spent making and selling things to high schoolers, yet the concept of a teenager didn't exist before 1922. 

In other words, our definition of childhood is not an ever-fixed star. It is a social construct that changes to reflect the norms and standards of the time. 

The Endless Journey

Whatever we choose to label those in the final plane, we know it is a period of relative calm and maturity marked by a desire to find one's place in society. Montessori described it as a time "when the individual can develop the spiritual strength and independence for a personal mission in life." 

In keeping with the patterns of the first three planes, the fourth plane covers a six year period. However, the actual end of the fourth plane is a matter of debate. Some researchers argue it ends sometime between twenty-four and thirty. Others argue there is not an ending so much as a fading into older life. The aching and stretches of childhood simply become part of the past and are no longer relevant. 

The road to adulthood is long but the journey of the soul never ending.