Council of Trent: Session XXIII, Holy Orders, Chapter II

CHAPTER II. On the Seven Orders.

And whereas the ministry of so holy a priesthood is a divine thing; to the end that it might be exercised in a more worthy manner, and with greater veneration, it was suitable that, in the most well-ordered settlement of the church, there should be several and diverse orders of ministers, to minister to the priesthood, by virtue of their office; orders so distributed as that those already marked with the clerical tonsure should ascend through the lesser to the greater orders. For the sacred Scriptures make open mention not only of priests, but also of deacons; and teach, in words the most weighty, what things are especially to be attended to in the Ordination thereof; and, from the very beginning of the church, the names of the following orders, and the ministrations proper to each one of them, are known to have been in use; to wit those of subdeacon, acolyth, exorcist, lector, and door-keeper; though these were not of equal rank: for the subdeavonship is classed amongst the greater orders by the Fathers and sacred Councils, wherein also we very often read of the other inferior orders.

Translation: J. Waterworth, The Canons and Decrees of the Council of Trent (1848), Hanover Historical Texts Project transcription (1995).