The act of making deep commitments to freely chosen responsibilities, whether public or private, choosing responsibilities allows a person to voluntarily accept responsibilities which they consider important and may involve work, service, relationships, or care for others. (p. 119, 273)

Encodings are durable, intrinsic capacities that shape how a person naturally operates and that become visible through life experiences. Encodings are discovered through experience and may remain hidden until circumstances bring them into view.

A dynamic process of continuing to grow while drawing on capacities developed earlier in life, “extending out” involves exploring new areas, learning, and experimenting, while “circling back” involves returning to and reapplying previously discovered encodings and capabilities. (p. 118, 247)

Flipping the arrow of money is the mental shift from seeing work primarily as a means to make money to seeing money as a resource that enables a person to do work aligned with their encodings. For the people in the author’s study of individuals who found deep engagement in their work, money became a means to pursue their hedgehog, instead of the primary goal itself. (p. 24, 99)

Fog is a phase of uncertainty, confusion, or disorientation about the best path forward, often following a major cliff. The author describes fog as a normal part of life that can affect even the most accomplished people at any stage. (p. 8, 157)

One of the three core elements of a personal hedgehog, “inner fire” describes an intense, intrinsic compulsion for an activity that is so engaging it feeds one’s energy and helps sustain engagement over time. Channeling this enthusiastic energy in alignment with one’s encodings focuses the inner fire on a particular activity or pursuit. (p. 25, 113)

A personal hedgehog is an arena of activity that integrates three elements: It aligns with your encodings (durable, intrinsic capacities you discover through experience), you can flip the arrow of money (treat money as fuel for the work instead of its primary goal) to pursue it, and it focuses your inner fire (an intrinsic compulsion so engaging it replenishes your energy). To be “in hedgehog mode” (264) is to commit to organizing your life around this One Big Thing for an extended period.

“Return on luck” is the concept that what matters is not simply the luck (good or bad) that happens to a person, but what they do with it. The author distinguishes luck itself—an unpredictable event largely beyond one’s control—from the “return on luck” (229), which is how a person responds to and makes use of that event.

A serial hedgehog is a life pattern where a person discovers and moves on to a second (or even a third) personal hedgehog across their life. About half the people in the author’s study followed this pattern, making major transitions into new arenas of activity later in life.

An iterative, often unplanned method for navigating through fog, “simplex stepping” is a series of small, “next best steps” (185). This approach allows for forward movement and discovery without needing a clear long-term plan or final destination.