The piece nobody has written yet because they'd need to have read Lowry's The Essence of Budo (2010), Stevens on Tesshu's Sword of No Sword, David Whyte's body-as-membrane work in his Perell interview, and the Funakoshi-carried-up-stairs anecdote in the same week is:
The Practitioner's Decade — what happens to mastery at the precise moment the body starts failing.
Most disciplines have a developmental arc that assumes intact instruments — intact bodies, intact memory, intact peak performance windows. The retirement model that follows is: do the work, accumulate skill, then stop and enjoy the accumulated results.
A different developmental arc — visible only in disciplines with long lifelong-practice tradition — assumes the instrument will fail and asks what carries the practice through the failure. Lowry's damashi is the explicit theory: a practitioner-spirit substrate built by long practice that survives illness, age, accident. Tesshu's zensho ("live completely / die completely") is the same phenomenon at terminal-state level. Whyte's body-as-membrane is the opposite theory — locating practitioner-substance in the intact body, requiring the body to function for the practice to work.
The piece would put these in conversation. The Funakoshi case (carried up dojo stairs in old age, still teaching) is the demonstration of one trajectory. The retired athlete is the demonstration of the other. The novelist who can no longer write but who can still mentor is somewhere between. The aging surgeon whose hands fail is somewhere else.
The thesis: every long discipline has a decade — typically somewhere between 60 and 80, sometimes earlier — when the body or cognition starts failing and the practitioner discovers whether the practice built something that survives the failure or whether the practice WAS the body's prime years. The disciplines that build damashi-equivalents produce practitioners who continue. The disciplines that depend on intact instruments produce retirees.
The piece requires all four sources in dialogue:
No single source produces the argument. Without Lowry, the framework has no name. Without Tesshu, the framework has no terminal-state articulation. Without Whyte, the opposing position can be straw-manned. Without Funakoshi, the abstract argument has no anchor.
The natural audience is mid-career professionals (40s and 50s) who are starting to wonder which of their current practices will carry them into old age. The piece would resist:
The piece would attract: practitioners of long disciplines (contemplative, scholarly, monastic, certain craft traditions) who already know the trajectory but haven't seen it named cross-culturally.