“By pursuing this process, a man sooner or later discovers that he is the master-gardener of his soul, the director of his life. He also reveals, within himself, the laws of thought, and understands, with ever-increasing accuracy, how the thought-forces and mind elements operate in the shaping of his character, circumstances, and destiny.”

To illustrate the power of thought, Allen uses a metaphor comparing people’s power over their lives to a master-gardener’s power over a garden. Allen’s central assertion in As a Man Thinketh is that people shape their characters and life circumstances through the quality of their thoughts.

“The outer world of circumstance shapes itself to the inner world of thought, and both pleasant and unpleasant external conditions are factors, which make for the ultimate good of the individual.”

Allen further elaborates on the connection between the external and internal worlds, illustrating that one cannot think negative thoughts without experiencing negative outcomes in their lives. A person can grow and better their life only by thinking positive thoughts and directing those thoughts toward righteous goals and purposes.

“Men do not attract that which they want, but that which they are. Their whims, fancies, and ambitions are thwarted at every step, but their inmost thoughts and desires are fed with their own food, be it foul or clean.”

Allen engages with mesmeric ideals of attraction in describing how people’s attitudes and thoughts create their life experiences. People who practice positive thinking experience righteous outcomes because people attract what they “are,” and Allen establishes early in the book that people are what they think.