A vast divide may separate what is possible and what is probable.
Attorney General Chris Koster has advanced the idea of reviving use of a gas chamber to carry out Missouri executions.
The concept is possible; state statutes list death by gas as one of two execution options. The other is lethal injection.
As a practical matter, however, reintroduction of a gas chamber is not likely.
Missouri no longer has an operational gas chamber. The device used to execute 39 death row inmates between 1938 and 1965 now is a tourist attraction. The defunct gas chamber is among the most popular stops on tours of the vacated Missouri State Penitentiary.
Can the old gas chamber be retrofitted and transported? Can a new one be purchased, and at what cost?
Answers to those questions are worth exploring only after affirming that reintroduction of death by gas is feasible and desirable.
Koster raised the idea because the use of lethal injection has been stalled. The impediment is a court battle about whether lethal injection violates the constitutional prohibition against "cruel and unusual punishment."
As the protracted fight continues, available lethal injection drugs have reached their expiration dates, leaving a dwindling supply.
But any plans to revive use of a gas chamber also would raise objections that it constitutes cruel and unusual punishment.
Koster addressed those objections when he said: "The premeditated murder of an innocent Missourian is cruel and unusual punishment. The lawful implementation of the death penalty, following a fair and reasoned jury trial, is not."
Courts judge the circumstances - including cruelty - of a murder to determine punishment.
Separately, courts must decide the cruelty of a punishment to determine constitutionality.
Bringing back the gas chamber invariably will invite more challenges in the courts.
And we will be back to where we are now - impatiently awaiting a ruling on whether executions may proceed.