In response to charges brought up by the web site referenced in the blog below (as well as other criticisms), I figured I should touch on some common misconceptions and, frankly, illusions about the beliefs of C.S. Lewis.
This will be in Q&A format, and for the most part, I will allow Lewis's words to speak for themselves.

Q Did Lewis believe in "more than one way" to God? Or, Does Lewis believe that non- or un- Christian belief, if held sincerely, will or can lead to God?

A

I think we must attack wherever we meet it the nonsensical idea that mutually exclusive propositions about God can be true.
-- from ?Christian Apologetics?

Also:

We are told that Christ was killed for us, that His death has washed out our sins, and that by dying He disabled death itself. That is the formula. That is Christianity. This is what has to be believed.
-- from Mere Christianity

That seems unequivocal to me.
Also, if Lewis believed all men, or even men of sincere faiths other than Christianity, would eventually be saved, why then did he say this:

Woe to you if you do not evangelize.
-- from ?Modern Theology and Biblical Criticism?

Q Was Lewis a universalist? Was he an inclusivist?

A The first question asks if Lewis believed all men will be saved regardless of belief. The answer is no, and there is absolutely no support for this view. One of Lewis?s foremost literary influences was George MacDonald, who may actually have been a universalist, so perhaps the confusion comes from this connection.

The second question asks if Lewis believed some men may be saved by Jesus even if they do not believe specifically in Christianity. My answer is no.
There is a better case for this charge, but I do not think it holds up. The primary argument uses a passage in the children?s novel The Last Battle. Once again, it is unwise to make a specific theological charge based on an ambiguous literary reference. More than likely, the passage is a reflection of Lewis?s belief in mythology carrying ?scattered truth? that foreshadows the real Truth. Lewis called Christianity ?Myth Become Fact? in an essay of the same name in God in the Dock.
Other than this brief exchange in the novel, though, there is no other direct evidence that Lewis anyone could be saved other than through specific belief in Jesus Christ.

Q Did Lewis believe faith + anything equaled salvation? Or, Did Lewis espouse a ?works evangelism??

A

The Christian is in a different position from other people who are trying to be good. They hope, by being good, to please God if there is one; or ? if they think there is not ? at least they hope to deserve approval from good men. But the Christian thinks any good he does comes from the Christ-life inside him. He does not think God will love us because we are good, but that God will make us good because He loves us.
-- from Mere Christianity

Q Did Lewis espouse a saving sacramentalism?

A Lewis said very little about the Eucharist. What words on it I have found were not ?questionable,? and they certainly did not imply a salvific communion.
Of baptism, Lewis writes:

Don?t bother at all about that question of a person being ?made a Christian? by baptism. It is only the usual trouble about words being used in more than one sense. Thus we might say a man ?became a soldier? the moment that he joined the army. But his instructors might say six months later ?I think we have made a soldier of him.? Both usages are quite definable, only one wants to know which is being used in a given sentence.

There is of course a lack of specificity here. But nowhere else do we see Lewis prescribe baptism as ?how one is saved.? At the most, perhaps, he sees baptism as a necessary component of the work of salvation. But that is not the same thing as salvation itself.
Moreover, any claim that Lewis viewed baptism as Catholics do has no evidence to support it.

Q Did Lewis believe in Purgatory?

A No and yes.
No, I do not think it is evident that Lewis believed in purgatory, in the Roman Catholic sense. Most critics who make this charge draw largely from the novel The Great Divorce. This is shoddy deduction, to say the least. And notice that none of these same critics say Lewis believes in ghosts or the transmigration of souls or any other vehicle of fantasy in the fictitious work.

But, yes, Lewis does believe in a purgatory. Here is what he says:

I believe in Purgatory.
Mind you, the Reformers had good reasons for throwing doubt on ?the Romish doctrine concerning Purgatory? as that Romish doctrine had then become . . .
. . . Our souls demand Purgatory, don?t they? Would it not break the heart if God said to us, ?It is true, my son, that your breath smells and your rags drip with mud and slime, but we are charitable here and no one will upbraid you with these things, nor draw away from you. Enter into the joy?? Should we not reply, ?With submission, sir, and if there is no objection, I?d rather be cleaned first.? ?It may hurt, you know? ? ?Even so, sir.?
-- from Letters to Malcolm: Chiefly on Prayer

It is clear from this passage that Lewis did not believe in a geographic purgatory. Notice his affirmation of the Reformation rejection of the Roman view.
What Lewis is mentioning here, I believe, is a finality to the process of sanctification. He evidently believed that we will require a final ?purging? prior to entering Paradise. This may be equivalent to the idea of receiving a new, glorified body. Maybe not.
I think Lewis?s words are ambiguous, but nevertheless do not see any support in them for attributing the Catholic view of Purgatory to him. (Not that, if it were true, it would make him any less a true Christian or any less an incredible scholar.)

Some may also make this claim based on Lewis?s undeveloped thoughts on Hell. But even this is not evidence of heresy or apostasy or even liberality. Many conservative evangelicals differ on what hell will be like. It is enough for me that Lewis believes in such a place and that those who do not believe in Jesus end up there:

I don?t think we know the details; we must just stick to the view that (a) all justice and mercy will be done, (b) but nevertheless it is our duty to do all we can to convert unbelievers.
-- from Letters of C.S. Lewis

Q Was Lewis a Taoist?

A This is perhaps the dumbest charge made (see another article in the web site linked to below in which this specific claim is made).
No, Lewis was not a Taoist. I assume people see him using the word and promoting the idea of ?the Tao? in The Abolition of Man and just assume he is espousing Eastern mysticism. This is akin to seeing the phrase ?meditation on the Word? and accusing the author of Buddhism.
The Tao of Lewis has nothing to do with the Eastern religion Taoism. I am not certain, but I don?t think the word ?Taoism? even appears in the book. What Lewis has in mind by ?Tao? is the English translation ?Way,? which is what he uses for the concept of universal, moral absolutes. Every Christian should believe this. Moral absolutes are what bind society together; they are what our laws are ultimately based upon.
It has nothing to do with Eastern mysticism and everything to do with absolute truth. Here is what Lewis writes:

This thing which I have called for convenience the Tao, and which others may call Natural Law or Traditional Morality, . . . is not one among a series of possible systems of value. It is the sole source of all value judgements. If it is rejected, all value is rejected. If any value is retained, it is retained.
-- from The Abolition of Man

Also:

[The Tao is] the doctrine of objective value, the belief that certain attitudes are really true, and others really false, to the kind of thing the universe is and the kind of things we are.
-- from The Abolition of Man

Lewis?s Tao is just a fancy way to say objective and absolute truth.

I hope these answers, some in Lewis?s own words, may suffice in responding to the theological criticism of him. (Also see Bill's fine comments in the blog comments thread below).
Lewis never claimed to be a systematic theologian, nor even a minister. He converted to Christianity as an adult and much of his ideas of faith was refined from the point of view of a literary scholar and philosophical mind. I happen to think he excelled at all he undertook.
Many of these charges are based on ambiguous prooftexts, brief passages in works of fiction, vague lines in personal correspondence, or ? most often ? misunderstandings of what he is really saying.

I have always in my books been concerned simply to put forward ?mere? Christianity.
-- from Letters of C.S. Lewis

It is a shame that narrow minded persons have so much zeal for accentuating non-essentials and passing them off as legalities, and that they believe Lewis?s failure to do the same constitutes heresy, apostasy, satanism, mysticism, or what-have-you. Why he owes them something more than orthodox Christianity is beyond me.