Yards from my front door are the birthplace and boyhood chapel of Dr James Martineau (1805-1900) who won the gratitude and admiration of many non-Unitarians for his strong and ardent Deism.

In a world shaken by Darwin, he argued powerfully for the existence of a transcendent and personal God. By respecting and accommodating the new insights, he helped many to keep the Faith.

This is the sixth in a set of reflections (July, September, December, January and earlier this month) prompted not by the Darwin celebrations but by a broadside delivered in a pub by an unbelieving friend.

He's still unbelieving - and still a friend. Friendship is too important to let religion damage.

Yet St Peter insisted: "Be ready always to give an answer to every man that asketh you a reason of the hope that is in you."

In responding to one friend, at the start of this mini-series, I provoked another. He ridiculed my attempts to show that religious belief was consistent with intellectual integrity.

"A hopeless task," he wrote, and quoted St Paul. I sympathised. For us to get a handle on God is like fishermen trying to haul the sea into the boat. But I want to be able to take my brain to church.

Anyhow, he'd missed the point. Paul inhabited a world which believed in the gods. We don't. We can preach till we're blue in the face, but if people don't really believe in the existence of God, we're wasting our time. That's our predicament.

However, if we define 'God' as Ultimate Reality, the Irreducible, the Energy which upholds matter, or as That-in-which-all-things-consist, animate and inanimate, the focus of the discussion shifts. The crucial question becomes not "Does God exist?" but "Is God 'personal' - and, in any sense, 'knowable'?"

I'm not convinced that the primeval soup invented itself, nor that energies evolving wholly at random produced beings capable of displaying self-sacrificial compassion, composing The Pathetique, or wrestling with conscience.

Certainly, the creature cannot be greater than the Force which sustains it. 'Ultimate Reality' must embrace everything we mean when we use the word 'person'.

But intimate knowledge of such an Unimaginable Vastness would destroy us. Glimpses of God are possible only because God reveals his presence.

The channels of this self-disclosure - Church, Bible, history - invite rigorous study. Upon it our knowledge of Jesus Christ depends.

But, there, Reason's unaided work ends. Now, Intuition and Will must play their part. For the understanding we acquire by 'studying Jesus' elicits knowledge of a different kind: self-knowledge, whose truth is not proven but recognised. Moreover, these personal perceptions demand a verdict. A positive response to this kind of knowledge is called 'faith'.

When Christ's vision of a Kingdom of Love rings true, and we want to be part of it - that's faith.

Faith is neither blind nor static, but possesses its own dynamism. It is based upon evidence and experience, needs to be informed and nourished, burns low - then rises to a flame.

'Man come of age' doesn't mean we can manage without religion. True maturity includes the humility to recognise our frailty, and the ability to co-exist with our doubts and hopes.

Religion transcends reason. To believe in God is not irrational and worship is an adult activity. Holy Week and Easter beckon - the perfect season to re-engage in the adventure of faith.

Isaac Watts wrote: "Where reason fails, with all her powers/ There faith prevails and love adores." Wesley added:

"Faith lends its realising light,

The clouds disperse, the shadows fly;

The Invisible appears in sight,

And God is seen by mortal eye."