This is the same as with faith. For what else does the Word teach except faith and charity, the two essentials for salvation? We read:

You are to love the Lord with all your heart and with all your soul, and your neighbour as yourself. Matt. 22:34-39.

And Jesus said, I give you a [new] commandment, to love one another. By this you will be known to be my disciples, by loving one another. John 13:34, 35; similarly 15:9; 16:27.

We also read that man is to bring forth fruit like a good tree; and that those who do good deeds will be rewarded at the resurrection [Luke 14:14]; and many similar statements. What would be the point of them if a person could not display charity of himself, or acquire it for himself in any way? Surely he can give alms, help the needy, and do good deeds in his home or at his work? Surely he can live in accordance with the Ten Commandments? Has he not got a soul to make him act like this, and also a rational mind which can induce him to act for some purpose or other? Surely he can think that he will do* these actions because they are enjoined in the Word, and so by God? There is no one who lacks this ability; and the reason for its not being lacking is that the Lord confers it on everybody, and He confers it as if it were something of the person's own. For is there anyone who when he does a charitable act is aware of doing it otherwise than of himself?

* Reading facturus for fructurus, which makes no sense.