Christians have often disputed as to whether what leads the Christian home is good actions, or Faith in Christ . . . It does seem to me like asking which blade in a pair of scissors is most necessary . . . Good actions . . . done with the idea that Heaven can be bought, would not be good actions at all . . . If what you call your 'faith' in Christ does not involve taking the slightest notice of what He says, then it is not Faith at all -- not faith or trust in Him, but only intellectual acceptance of some theory about Him.
The Bible really seems to clinch the matter when it puts the two things together into one amazing sentence. The first half is, 'Work out your own salvation with fear and trembling' -- which looks as if everything depended on us and our good actions: but the second half goes on, 'For it is God who worketh in you' [Phil 2:12-13] -- which looks as if God did everything and we nothing . . . You see, we are now trying to understand, and to separate into water-tight compartments, what exactly God does and what man does when God and man are working together. And, of course, we begin by thinking it is like two men working together, so that you could say, 'He did this bit and I did that.' But this way of thinking breaks down. God is not like that. He is inside you as well as outside: even if we could understand who did what, I do not think human language could properly express it. In the attempt to express it different Churches say different things. But you will find that even those who insist most strongly on the importance of good actions tell you you need Faith; and even those who insist most strongly on Faith tell you to do good actions. At any rate that is as far as I go.
(Mere Christianity, New York: Macmillan, 1952, 129-130)