“And greater works than these shall he do.” Than what, pray? Shall we say that one is doing greater works than all that Christ did who is working out his own salvation with fear and trembling? A work which Christ is certainly working in him, but not without him; and one which I might, without hesitation, call greater than the heavens and the earth, and all in both within the compass of our vision.
And it is assuredly something less to preach the words of righteousness, which He did apart from us, than to justify the ungodly, which He does in such a way in us that we also are doing it ourselves.
[St. Augustine, Tractate on John 72.3]
Infused virtue is caused in us by God without any action on our part, but not without our consent. This is the sense of the words, "which God works in us without us." As to those things which are done by us, God causes them in us, yet not without action on our part, for He works in every will and in every nature. [St. Thomas Aquinas, ST I-II Q55 A4 ad 6]