The Apostle says (Romans 6:23): "The grace of God is life everlasting." And as a gloss says, this is said "that we may understand that God, of His own mercy, leads us to everlasting life." [ST I-II, Q109, A5]If the grace of God is eternal life, then eternal life cannot be merited; it must be received. One reason for this (as we have seen) is that our final End (the Beatific Vision) is beyond our finite, mortal powers:
Acts conducing to an end must be proportioned to the end. But no act exceeds the proportion of its active principle; and hence we see in natural things, that nothing can by its operation bring about an effect which exceeds its active force, but only such as is proportionate to its power. Now everlasting life is an end exceeding the proportion of human nature, as is clear from what we have said above (Question 5, Article 5[which we have already examined - RdP]).It is not possible for us to merit that which is beyond our powers:
Hence man, by his natural endowments, cannot produce meritorious works proportionate to everlasting life; and for this a higher force is needed, viz. the force of grace. And thus without grace man cannot merit everlasting life; yet he can perform works conducing to a good which is natural to man, as "to toil in the fields, to drink, to eat, or to have friends," and the like...But we can never merit salvation by our works themselves. That which makes them meritorious is not that they are ours, but that God has given us grace: as St. Augustine has said:
no one merits the grace which brings them to attain to justice; our prayer is a gift; no one merits justification; no one merits Faith, which is a gift, without which no one does good; love is given by God; our merits are gifts effected through grace; when God rewards, He crowns His gifts, even the merits He has given; eternal life is a grace... [Letter 194; emphasis added]The Catholic view of our salvation is that we are saved by grace alone, notwithstanding the erroneous misinformation that is spread by the enemies of the Church.