The engineer volunteered to instruct me in the problem. I took up the blocks and began trying to unite them. As one difficulty after another arose, I was given instruction in the principle for overcoming it. No principle was presented to me till I had faced a situation demanding that particular principle. The practice and the theory went together, and so far as the instruction was concerned the practice preceded the theory step by step. I was therefore employing the Practical-theoretical method. As a result I was enabled to solve the problem in fifteen minutes. Furthermore I knew just how I had done it and could do it again and could apply the same principles to other puzzles. A comparison of these results is most instructive. The lad who went at it blindly by the Haphazard method required eight hours and even then did not analyze out the principles that would help him solve later prob- <p 269> lems. My son, who employed the Apprenticeship method, accomplished his task in two hours but discovered no principles. His work was blindly mechanical. The engineer worked according to the Theoretical-practical method, completed his task in thirty minutes, and understood perfectly what he had done. By employing the Practical-theoretical method I was enabled to accomplish the task in fifteen minutes and to understand also how it was done. Whether I have in mind my own development or that of my employees, if I am seeking to utilize the Practical-theoretical method of capitalizing experience, I am confronted with two problems: (1) How shall I secure or provide the requisite practical experiences? (2) How shall I secure or provide the appropriate theoretical interpretation of such experiences? During recent years in the educational, industrial, and commercial world serious attempts have been made to answer these two questions, and the results are most significant. <p 270>