Our readings this week are Isaiah 40.12–17, 27–end and Matthew 28.16–20.

This Sunday is Trinity Sunday, so perhaps it's no surprise that our reading from Isaiah points out to us, in no uncertain terms, our inability to understand and grasp the fullness of God.

It's also why the Matthew reading will have been chosen - as it's one of the very few places in Scripture where we find an explicit trinitarian formula of 'Father, Son, and Holy Spirit'.

To me, this week, though, the more fitting complement to Isaiah is the extraordinary report in Matthew of the disciples' faith - or rather lack of it: 'When they saw him, they worshipped him; but some doubted.'

In the literal presence of the risen Christ 'some doubted!'  Yet they still received his commission, and they still went out and changed the world.  If that doesn't give you hope, I don't know what will.

Doubt, it appears, is not the opposite to faith - it doesn't preclude worship, and it doesn't negate discipleship.  If anything it is the germ of honesty that makes the whole of faith rise in the marvellous thing it is.  Because the reality is faith can only exist with doubt - or something very like it - in it.  As Isaiah points out, God is so far beyond our comprehension - in terms of our capacity to understand, and even to perceive - how can we ever know enough to know it all, so as to be certain?

Certainty is the opposite of faith, not doubt.  And often is it not certainty that lies behind so many of the horrors committed in the name of faith?  Certainty that I'm right, and you're wrong; that I'm 'saved', and you're 'damned'; that I'm of value, and you're of use...

Our faith is not strongest when we are most certain, it is strongest when we are most trusting.  Because that is what faith is: trusting in a reality we cannot fully perceive, and discovering its truth in the ways it shapes us and the world around us.

It was trust, faith - in the person of Jesus, and his promise to be with them to the end of the age - that powered those earliest disciples, and changed their world.  It is the same trust that can transform us.

That is if I'm right, which, of course, I might not be.  Glorious isn't it?