Now because those who receive a revelation from God ought in the order of divine enactment to instruct others, there needed to be further communicated to them the grace of speech. Hence it is said: The Lord hath given me a learned tongue (Isai. L, 4): I will give you speech and wisdom, which all your adversaries shall not be able to withstand and gainsay (Luke xxi, 15). Hence also the gift of tongues (Acts ii, 4).
But because any announcement put forth requires confirmation before it can be received, -- unless indeed it is self-evident, and the truths of faith are not evident to human reason, -- there was need of something to confirm the announcements of the preachers of the faith. But, inasmuch as they transcend reason, they could not be confirmed by any demonstrative process of reasoning from first principles. The means therefore to show that the announcements of these preachers came from God was the evidence of works done by them such as none other than God could do, healing the sick, and other miracles. Hence the Lord, sending his disciples to preach, said: Heal the sick, raise the dead, cleanse lepers, cast out devils (Matt. x, 8); and, They going forth preached everywhere, the Lord working withal, and confirming their words by the signs that followed.*
In the aforesaid effects of grace we observe a certain difference. Though the name of 'grace' applies to them all, inasmuch as they are given 'gratuitously' without any preceding merit, nevertheless the working of love alone has a further claim to the name of 'grace,' as constituting the subject in 'the state of grace,' or in 'the good graces of God' (gratum Deo facit): for it is said: I love them that love me (Prov. viii, 17). Hence faith and hope and other means to the last end may be in sinners, who are not in the grace of God: love alone is the proper gift of the just, because he who abideth in charity abideth in God, and God in him (1 John iv, 16).*
There is another difference to be observed in these workings of grace, and it is this, that some of them are necessary for a whole lifetime, as believing, hoping, loving, and obeying the commandments of God, without which things salvation is impossible; and for these effects there must be in man certain habitual perfections, that he may be able to act according to them as occasion requires.* Other effects of grace are necessary, not for a whole lifetime, but at certain times and places, as working of miracles, or foretelling of future events. To these effects habitual perfections are not given, but certain impressions are made by God, which cease when the act ceases, and have to be repeated when the act is repeated. Thus prophets in every revelation are illumined with a new light; and in every working of miracles there must be a fresh putting into operation of divine power.*
3.154 : That Divine Grace causes in us a Hope of future Blessedness
3.156 : That Man needs the Assistance of Divine Grace to Persevere in Good