The interpretation timeline

The Second Council of Lyons

Effected a temporary reunion with the Greek Church, and added the word filioque to the creed of Constantinople.

1274 Lyons
Held by
Pope Gregory X
Present
the Patriarchs of Antioch and Constantinople, 15 cardinals, 500 bishops, and more than 1,000 other dignitaries
What it did
effected a temporary reunion of the Greek Church with Rome; the word filioque was added to the symbol of Constantinople; laid down the rules for papal elections

These facts as given by the Catholic Encyclopedia (1913), "Councils" PD

Scholastic

c. 1100 – 1500
1274
Event
The Second Council of Lyons

Lyons II adds the word filioque to the creed of Constantinople, and effects a reunion with the Greek Church that does not hold.

1274
A.D.
“With faithful and devout profession we confess that the Holy Spirit proceeds eternally from the Father and the Son, not as from two principles but as from one principle, not by two spirations but by a single spiration. This the most holy Roman Church, mother and teacher of all the faithful, has professed, preached and taught until now; this she firmly holds, preaches, professes and teaches. This is the unchangeable and true judgement of the orthodox Fathers and Doctors, Latin and Greek alike. But because some, through ignorance of the aforesaid irrefutable truth, have fallen into various errors, we, desiring to bar the way to errors of this kind, with the approval of the sacred Council condemn and reprove those who shall presume to deny that the Holy Spirit proceeds eternally from the Father and the Son, or who with rash daring shall assert that the Holy Spirit proceeds from the Father and the Son as from two principles and not as from one.”
Fideli ac devota professione fatemur, quod Spiritus Sanctus aeternaliter ex Patre et Filio, non tanquam ex duobus principiis, sed tanquam ex uno principio, non duabus spirationibus, sed unica spiratione procedit: hoc professa est hactenus, praedicavit et docuit, hoc firmiter tenet, praedicat, profitetur et docet sacrosancta Romana Ecclesia, mater omnium fidelium et magistra: hoc habet orthodoxorum Patrum atque Doctorum, Latinorum pariter et Graecorum incommutabilis et vera sententia. Sed quia nonnulli propter irrefragabilis praemissae veritatis ignorantiam in errores varios sunt prolapsi Nos huiusmodi erroribus viam praecludere cupientes, sacro approbante Concilio, damnamus et reprobamus, qui negare praesumpserint, aeternaliter Spiritum Sanctum ex Patre et Filio procedere: sive etiam temerario ausu asserere, quod Spiritus Sanctus ex Patre et Filio, tanquam ex duobus principiis, et non tanquam ex uno, procedat.
Source
Modern · 1953 →

The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.