From Mere Christianity by C.S. Lewis (if you've never read it, do! It changed my life, it might yours!). Seemed appropriate for today's Feast of Christ the King and this last week of the liturgical year.
Why is God landing in this enemy-occupied world in disguise to start a secret society to undermine the devil? Why is He not landing and invading it? Is it that He is not strong enough? Well, Christians think that He is going to land in force; we do not know when, but we can guess why He is delaying. He wants to give us the chance of joining His side freely. I do not suppose you and I would have thought much of a Frenchman who waited till the Allies were marching into Germany and then announced he was on our side. God will invade. But I wonder whether people who ask God to interfere openly and directly in our world what it will be like when He does. When that happens it is the end of the world. When the author walks onto the stage, the play is over. God is going to invade alright: but what is the good of saying you are on His side then, when you see the whole natural universe melting away like a dream and something else -- something it never entered your head to conceive -- comes crashing in; something so beautiful to some of us and so terrible to others that we will have no choice left? For this time it will be God without disguise; something so overwhelming that it will strike either irresistible or irresistible horror into every creature. It will be too late then to choose your side. There is no use saying you choose to lie down when it has become impossible to stand up. That will not be the time for choosing: it will be time we discover which side we have really chosen, whether we realized it before or not. Now, today, this moment, is our chance to to choose the right side. God is holding back to give us that chance. It will not last for ever. We must take it or leave it.