But _prayer considered in itself_ cannot be so continuous; for we must needs be occupied with other things. Hence S. Augustine says in the same place: "At certain intervals, at divers hours and times, we pray to God in words so that by these outward signs of things we may admonish ourselves, and may learn what progress we have made in this same desire, and may stir ourselves up to increase it." But the quantity of a thing has to be determined by its purpose, just as a draught has to be proportioned to the health of the man who takes it. Consequently it is fitting that prayer should only last so long as it avails to stir up in us this fervour of interior desire. And when it exceeds this measure, and its prolongation only results in weariness, it must not be prolonged further. Hence S. Augustine also says to Proba: "The Brethren in Egypt are said to have had frequent prayers; but they were exceedingly brief, hardly more than eager ejaculations; and they adopted this method lest, if they prolonged their prayer, that vigilant attention which is requisite for prayer should lose its keen edge and become dulled. And thus they clearly show that this same attention, just as it is not to be forced if it fails to last, so neither is it to be quickly broken off if it does last." And just as we have to pay attention to this in our private prayers, and have to be guided by our powers of attention, so must we observe the same principles in public prayer where we have to be governed by the people's devotion. Some, however, argue that our prayers ought not to be continual, thus: 1. Our Lord said[225]: _And when you are praying speak not much_. But it is not easy to see how a man can pray long without "speaking much"; more especially if it is a question of vocal prayer. But S. Augustine says to Proba: "To prolong our prayer does not involve 'much-speaking.' 'Much-speaking' is one thing; the unceasing desire of the heart is another. Indeed we are told of the Lord Himself that _He passed the whole night in the prayer of God_[226]; and, again, that _being in an agony He prayed the longer_,[227] and this that He might afford us an example." And Augustine adds a little later: "Much speaking in prayer is to be avoided, but not much petition, if fervent attention lasts. For 'much-speaking' in prayer means the use of superfluous words when we pray for something necessary; but much petition means that with unceasing and devout stirrings of the heart we knock at His door to Whom we pray; and this is often a matter rather of groans than of words, of weeping than of speaking."