Thémis
An old Greek word for the shared, mostly unspoken sense in any group of what is right — how power should be used, what each role owes and forbids. It names the moral background a community holds in common, broader than law and more particular than abstract ethics. The word matters because some accounts of moral injury define that injury as a betrayal of this shared order by someone in legitimate authority.
The Homeric Greek term that Jonathan Shay uses for the ordering of what's right — the shared, mostly unstated agreement in any social setting about what is fitting conduct, how authority should be exercised, what each role obliges and forbids. Shay's clinical definition of moral injury is betrayal of thémis in a high-stakes situation by someone who holds legitimate authority, and thémis is doing the technical work of the definition.
Etymology§
Θέμις in Homeric Greek — cognate with the verb τίθημι (to set, to place, to ordain) — names what is set down or laid out as the proper way of things. It is also the name of the goddess who personifies that ordering. In Homer the term refers to the customary moral order that holds a community together, including the norms governing relations between commander and warrior, host and guest, the living and the dead. Shay imports the term explicitly because contemporary English does not have a single word for this layered, mostly-tacit moral background, and the construct of moral injury depends on naming it.
For Shay, the betrayal that constitutes a moral injury is precisely the betrayal of thémis — not a violation of an explicit rule but the shattering of the unstated background expectation that authority will be exercised legitimately, that the community will hold to its own norms, that the soldier's good-faith participation will not be turned against him by his own side. The Homeric vocabulary is doing real analytic work here: thémis is broader than justice (δίκη), more particular than ethics, and inherently social — there is no thémis that an individual can hold privately apart from the community.
The technical role of the term is what marks Shay's definition off from Litz's reformulation. Litz's framework counts perpetration and witnessing as moral-injury-producing alongside betrayal, and treats the deeply held moral beliefs that get violated as if they were located inside the individual. Shay locates them in the community — in the thémis — and that location is what makes the injury, on his account, a wound to the relation between the individual and the group rather than to the individual alone.