Deus, in te sperantium fortitudo, invocantibus nostris adesto propitius, et, quia sine te nihil potest mortalis infirmitas, gratiae tuae praesta semper auxilium, ut, in exsequendis mandatis tuis, et voluntate tibi et actione placeamus.
Because of the word pairings fortitudo and infirmitas, voluntas and actio, a possible source for this Collect could be the anti-Pelagian writings of St. Augustine of Hippo (+430).
In classical Latin fortitudo rarely means just physical strength. Instead, it is “firmness, manliness shown in enduring or undertaking hardship; fortitude, resolution, bravery, courage, intrepidity”. In the Latin Vulgate of the Old Testment the Lord is often described as “my strength… fortitudo mea”. Latin and Greek Old Testament versions translate Hebrew maw’oz and ‘oz which indicate a place or means of safety, a refuge or stronghold. You probably know the great “battle hymn” of the 16th Protestant revolt in Germany, “Ein feste Burg ist unser Gott … A Mighty Fortress is our God”, the translation of a psalm by Martin Luther (+1546).
Since ancient times the battle of orthodox Catholicism with various heresies and schismatic movements has involved the use of hymns and songs. They help people learn and remember things. Augustine composed a song with sound theological points to combat the Donatists who had set up their schismatic altars against those of Catholics. This is true in more modern times as well. If the Lutherans had “A Mighty Fortress is our God” we Catholics had “Grosser Gott, Wir Loben Dich … Holy God, We Praise Thy Name” composed in 1774 as a paraphrase of the Te Deum going back to the late 4th or early 5th century, perhaps having a connection to St. Ambrose (+397).
Auxilium is “help, aid, assistance, support, succor”. The obsolete ICEL versions constantly had us asking for some “help” from God (who is, after all, really nice). In those now outdated prayers “help” was nearly always inadequate because the concept of “grace” was obliterated along with the word “grace” itself. Voluntas is mainly “will, freewill, wish, choice, desire, inclination”. This is the power of our free will which together with our intellect distinguishes us from brute beasts. It can also be more simply an “intention” or something we interiorly “will”.
O God, strength of those hoping in You, graciously be present to us as we are invoking You, and, because without You mortal weakness can do nothing, grant always the help of Your grace, so that, in the performance of Your commands, we may please You both in will and in action.
OBSOLETE ICEL (1973):
Almighty God, our hope and our strength, without you we falter. Help us to follow Christ and to live according to your will.
That was a good example of why we needed a new translation.
CURRENT ICEL (2011):
O God, strength of those who hope in you, graciously hear our pleas, and, since without you mortal frailty can do nothing, grant us always the help of your grace, that in following your commands we may please you by our resolve and our deeds.
In the fall of our First Parents, we were wounded and weakened in our intellect and will. It is hard for us to reason to what is good and true. After we figure them out with our reason or we learn about them from authority, because of our passions and appetites it can be hard for us to will to choose them. Our intellects and wills must be disciplined through the repetition of choices and actions in the right times, moments, and measures so that we develop good habits, virtues.
In our prayer voluntas is set in juxtaposition with actio “action”. We have “inclinations” to this or that thing. In actions our inclinations become concrete. Some actions are entirely mental or spiritual, in that they are actions of the mind. We have an initial idea or inclination and then we use our free will to grasp or refuse that idea. We can bring an inclination to a deeper thought, contemplate it. There are intellectual acts (for good or ill). There are also physical acts. We get an idea and then, with our intellects and wills, we figure out how to do it and choose to act (for good or ill). Because of the weakness in us from Original Sin, in order to will and act properly we must have the help of grace.
God begins and completes in us all the meritorious things we do. He gives us the strength to carry through with all good acts.