Praesta, quaesumus, omnipotens Deus: ut claritatis tuae super nos splendor effulgeat; et lux tuae lucis corda eorum, qui per gratiam tuam renati sunt, Sancti Spiritus illustratione confirmet.
Splendor and claritas are related to the concept of glory and of light. Illustratio is a technical term from ancient rhetoric. It is a “vivid representation” which, as it were, sheds light on the matter being discussed. It is an accurate rendering that echoes the reality of the original meant to make an impression, meant to make you see with your mind’s eye what is being described. How, this word has as its root yet another word for “light”.
Splendor… claritas… lux 2x… illustratio…
Confirmo is “to strengthen, establish”, or “to confirm” in the sense of give assurance, “to assert as true”. Again, there is a rhetorical or forensic overtone.
Grant, we beseech You, Almighty God, that the brightness of Your glory may shine upon us, and that the light of Your light may, through the enlightenment of the Holy Spirit, strengthen the minds of those who are reborn through Your grace.
Great, we implore, Almighty God, that the splendor of your glory shine forth upon us; and by the vivid light-shedding of the Holy Spirit may the light of Your light confirm the hearts of those who were reborn by Your grace.
A couple points to consider.
When Moses emerged from the cloud of the presence of God his face was so bright that it had to be covered with a veil. It was too bright to look at directly. God’s presence imparted to Moses something of its glory and Moses was transformed.
How much more will be be transformed when glorious risen in heaven and in the presence of God?
The rhetorical overtones of the vocabulary are probably not a coincidence. Rhetoric is used to move and to persuade and to edify. We use the words, the representations of a message we desire to impart to our listeners so that their minds and wills are conformed to the message.
Rhetoric is carried out mainly in the public square, the forum. It is “forensic“.
The Apostles, under the influence of the Holy Spirit, are changed from men hiding in their upper room to powerful preachers in the public square.
Like gerbils one day. Like lions the next.
They were “confirmed”. Their words and lives became an illustratio which pointed to the splendor of the truth.
Have you been confirmed?