In some ways it is a bit nit-picking to select short quotations from the lecture for comment - my apologies to the Cardinal for that; but the need to present a coherent and consistent understanding of what reason is, what faith is and, then, how the two relate to each other, appears to me vital to achieving a proper dialogue with atheism.
"Our faith is not founded on the conclusions of reason, but it is grounded in the Logos, the expressive Word that comes from God, and it is compatible with reasoned thought"
One might want to add to this that "the conclusions of reason" might provide some grounding for our faith, since reason is going to be very much to the fore in a dialogue with atheism, but Cardinal Murphy O'Connor is correct in asserting a decisive grounding in the revelation of God in the Word.
"We should remember that the proper response to God is that of faith, not absolute certainty".
The opposing of faith and certainty in this sentence is, I think, unfortunate; and the following discussion of Thomas Aquinas and Augustine reflects the unfortunate nature of the sentence. First of all, we need to be clear that faith can give a confident and certain knowledge of the truth contained in revelation - but some will read this sentence as a denial of that. That there is something more to be learnt about God, both intellectually and in terms of our lived communion with him, may be the intention of the "not absolute certainty" and be what Aquinas calls "imperfect knowledge", but that is not the same as questioning the confidence that we can have in the knowledge achieved through faith.
In his interview on Radio 4's Today programme, Cardinal Murphy O'Connor said:
"..reason of itself cannot prove the existence of God .."
" .. reason is not enough .."
The defined teaching of the Church is that we can come to a confident knowledge of God through the use of reason in studying the world around us. What faith, that is, the knowledge achieved through God's self-revelation, provides is another, complementary way in which this knowledge of God's existence can be known. In their different circumstances, people may in practice rely on one way of knowing more than they do on the other for their knowledge of God's existence, or they may not get there at all. But I think, in dialogue with atheism, religious believers are going to want to insist on the ability of reason to come to knowledge of God's existence.
"If Christians really believed in the mystery of God, we would realise that proper talk about God is always difficult, always tentative ... A God who can be spoken about comfortably and clearly by human beings cannot be the true God."
But the reference to God as mystery does not mean that what we say about God should not be said, or that we cannot have confidence in what we say about Him. It recognises that the revealed mystery of God is something to be lived as well as spoken about and known. The difficulty and tentativeness can refer to the what-is-still-to-be-learnt in our intellectual lives, but we need to be careful that it does not make a statement that we cannot really know about God at all.
The last part of this post is slightly adapted from the comment I sent earlier today to the "Debate" forum for this lecture on the Westminster diocesan website.
Reason can come to know things about the physical world around us (the physical sciences), about the human person and his presence in the world (the social sciences) etc. It can address questions about things that are not material - human motivations and consciousness. And from this, it can also address questions about the meaning of life, the universe and everything - and, whilst there is always more to be learnt or discovered, there is a possibility for confidence in this knowledge. And one can equally apply this reason to the phenomena of religion - it being profoundly irrational to deny the existence of religion as a phenomenon. An honesty in this study will not, in my view, permit the characterisation of religious belief as simply personal imaginings, its OK if you need it, invention of the early Church, etc. It is also necessary to understand what the term faith means - and again this has not been fully developed in the Cardinal's lecture. Faith is a knowledge that can be confident of what it knows in the same way that reason can be confident of what it knows, though the source of that knowledge is different. Yes, we can grow into greater knowledge, both reasoned and faith-based knowledge, but that is not the same as denying the confidence that we can have in both.
And, here I would want to endorse Cardinal Murphy O'Connor's call for greater dialogue between believers and non-believers. Let's undertake that through the hard work of applying our reason in all its many different approaches (the physical and social sciences) to the questions of atheism and religious belief. Religious believers are of the view that what we believe and teach can stand up to this challenge of reason; can the atheist position stand up to the same challenge?
As they say these days ... "bring it on".