A threefold error regarding prayer existed amongst the ancients; for some maintained that human affairs were not directed by Divine Providence; whence it followed that it was altogether vain to pray or to worship God; of such we read: _You have said, he laboureth in vain that serveth God_.[110] A second opinion was that all things, even human affairs, happened of necessity--whether from the immutability of Divine Providence, or from a necessity imposed by the stars, or from the connection of causes; and this opinion, of course, excluded all utility from prayer. A third opinion was that human affairs were indeed directed by Divine Providence, and that human affairs did not happen of necessity, but that Divine Providence was changeable, and that consequently its dispositions were changed by our prayers and by other acts of religious worship. These views, however, have elsewhere been shown to be wrong. Consequently we have so to set forth the utility of prayer as neither to make things happen of necessity because subject to Divine Providence, nor to suggest that the arrangements of Divine Providence are subject to change. To bring this out clearly we must consider that Divine Providence not merely arranges what effects shall take place, but also from what causes they shall proceed, and in what order. But amongst other causes human acts are causes of certain effects. Hence men must do certain things, not so that their acts may change the Divine arrangement, but that by their acts they may bring about certain effects according to the order arranged by God; and it is the same with natural causes. It is the same, too, in the case of prayer. For we do not pray in order to change the Divine arrangements, but in order to win that which God arranged should be fulfilled by means of prayers; or, in S. Gregory's words: "Men by petitioning may merit to receive what Almighty God arranged before the ages to give them."[111] Some, however, maintain that prayer is futile, thus: 1. Prayer seems to be necessary in order that we may bring our wants to the notice of Him to Whom we make the petition. But our Lord says: _Your Father knoweth that ye have need of all these things._[112] But it is not necessary for us to set forth our petitions before God in order to make known to Him our needs or desires, but rather that we ourselves may realize that in these things it is needful to have recourse to the Divine assistance. 2. Again, by prayer the mind of him to whom it is made is prevailed upon to grant what is asked of him; but the mind of God is unchangeable and inflexible: _The Triumpher in Israel will not spare, and will not be moved to repentance; for He is not a man that He should repent._[113] Consequently it is unavailing to pray to God. But our prayers do not aim at changing the Divine arrangements, but at obtaining by our prayers what God has arranged to give us.