The things which concerned him more than anything else were the what and the why—the what because he felt it was necessary to know absolutely what you were questioning and what you were doing or what concerned you, and then the why, the depth type of thinking which showed you the reason for doing the thing and would perhaps indicate clearly whether you should maintain what was being done or should change what was being done.

Lillian Moller Gilbreth (1962) Conference and Convention Proceedings American Institute of Industrial Engineers. p. 21.