You switch on the light and nothing happens. You drop a ball of paper into the rubbish bin, but it ends up on the opposite side of the room. You chop up an onion but the pieces won't come apart. You pour yourself a drink, but the liquid stays in the bottle.
If things were like this all the time, life would be unliveable. We rely on the laws of cause and effect in order to conduct our lives. If plants did not grow, we would have no food. If wheels did not turn, we would have no transport. We expect the shops to be open at predictable hours, and people to act in predictable ways.
The world that we live in, or, if you see it that way, the world God has provided for us to live in, is a world of firm and stable rules. We may not know them all - indeed, there may be too many for us to know, and there may be whole areas of which we have no idea. But we know enough to find a set of natural explanations for a light bulb not shining when it is switched on (and even for one shining when it is switched off!)
A lot of people expect prayer to be able to bend these rules. Jesus was clear that it cannot. "Can any of you by worrying add a single hour to your span of life?" (Matt 6:27). Jesus may well have said, "If you have faith the size of a mustard seed, you will say to this mountain, 'Move from here to there,' and it will move; nothing will be impossible for you." (Matt 17:20). But this was merely to emphasize the disciples' lack of faith, just as his remarks about camels and needles were to emphasize the obstacles wealth laid in the way of sharing God's kingdom.
If faith on its own cannot move mountains, if we live in a world where cause and effect are tightly linked, if things are going to happen whether we want them or not, what is the point of praying?
The answer lies in the nature of prayer. Prayer is talking with God. It can take many forms, of course, just as human conversation can consist of words of praise, of love, of confession, of concern for others, of baring our hearts to say what we want. There are differences from human conversation - there is no place for idle gossip or for passing on information, though we can share our reactions to pieces of news that affect us. But prayer can even contain words of anger, when those words bring to the fore our own disappointment ("My God, my God, why have you forsaken me?")
This talking can take place communally, when we gather together, or in private. "Whenever you pray, go into your room and shut the door and pray to your Father who is in secret; and your Father who sees in secret will reward you." (Matt 6:6). (Yet another example of Jesus' use of exaggeration! He is not condemning prayer in groups - just prayer for the wrong motives!)
The talk can often seem one-sided. God always listens, but only if we in our turn listen carefully can we hear God's answer. And if our prayers are for others, they too will hear the answer more easily if they listen. This does not mean our prayers for others have no effect unless the people we pray for are aware of them - but it helps!
If we see prayer as part of our relationship with God, the question of whether prayer "works" takes on a different meaning. God is not a supernatural on-line store, where we send in our orders and expect them to be delivered. In any case, our orders may well be for things which are bad for ourselves, or for other people. We tend to forget that praying for X to get that plum job also means praying that Y will not get it, that the mother praying for her son not to be killed in wartime should truly be a prayer that nobody gets killed. And asking God to move mountains (where to?) is asking to interfere with God's own creation, the natural order of things on which we all rely.
The prayer that "works" is the prayer that enables us to listen to God. And in terms of requesting, supplicating, interceding, our prayer should be modelled on the prayer that Jesus set as an example: the prayer that God's name should be held sacred over all the earth, that God's will should be done, and that we, and those around us, should not be tested beyond our powers. In all that we pray for, may our aim in praying be this and this above all: Thy Kingdom come!
HD