
In the recent film Conclave, the Dean of the College of Cardinals says: “Our faith is a living thing precisely because it walks hand in hand with doubt. If there was only certainty and no doubt, there would be no mystery—and therefore no need for faith.” Is this acceptable?
For the benefit of our readers, I should make clear that in the longer version of the question you sent, you mention that Bishop Robert Baron has condemned the film outright. That said, the question is a very good one, and one that many people have probably posed to themselves at one time or another.
We can start by reminding ourselves what faith is. As commonly understood, faith is the assent of the intellect to a truth, based not on the intrinsic evidence but on the authority of the one communicating it.
We have faith when someone has told us something for which we have no personal experience or evidence, and we believe it because we trust the person.
Thus, we can speak of human faith, when the person revealing the truth is human, and divine or theological faith, when the person revealing it is God.

When we think of it, practically everything we know, we know by faith. We know about other countries, when we haven’t visited them ourselves, because we have studied them in books or people who have been there have told us about them. We know about science because scientists have written about their discoveries and we believe them.
We know about current events in our own country or in other parts of the world because we have heard about them in the media.
It is reasonable to have this human faith because we trust people like our parents, teachers, historians, scientists, and even the media most of the time.
It is always reasonable to trust God himself, because he is truth itself, and he can neither deceive nor be deceived. In this sense the Catechism defines faith as “the theological virtue by which we believe in God and believe all that he has said and revealed to us, and that Holy Church proposes for our belief, because he is truth itself” (CCC 1814).
In all these matters, both human and divine, there is always an element of uncertainty, or obscurity, or what we might call doubt, because we have no direct evidence for what the other person is telling us.
If we had this evidence, we would no longer need faith. For example, we don’t need faith to know where we live, or who our parents and siblings are, because we have seen them for ourselves.

But we do need faith to believe that there are other cities or countries we have never visited, or to believe that there is a heaven and a hell, because we have never seen them personally.
So, coming back to your question, yes, our faith does walk hand in hand with doubt, in the sense of uncertainty, wonder, mystery. The very statement “If there was only certainty and no doubt, there would be no mystery… and no need for faith” implies that doubt in this case is to be understood as the lack of certainty.
This is very different from doubt as a voluntary act of the will which wilfully doubts, or questions some truth. Voluntary doubt implies that we do not trust the person revealing the truth.
Naturally, there might be good reason at times not to trust a particular human person, because they have shown themselves to be untrustworthy in the past.
But God, who is truth itself, can always be trusted and it would be a sin to doubt what he reveals.
The Catechism teaches: “There are various ways of sinning against faith: Voluntary doubt about the faith disregards or refuses to hold as true what God has revealed and the church proposes for belief.”
This is very different from involuntary doubt, which “refers to hesitation in believing, difficulty in overcoming objections connected with the faith, or also anxiety aroused by its obscurity” (CCC 2088).
In summary, faith walks hand in hand with doubt, when doubt is understood as uncertainty, or difficulty in believing some truth because of the lack of immediate evidence or because of its obscurity.