It depends on how you define faith. St. Thomas defines it as an opinion that reaches the certainty of knowledge by an act of will. In other words, you have good reasons to believe but not 100% certainty. But your will is drawn by the goodness of the Faith and so you choose to commit yourself entirely to believing. That at least is how I understand his discussion of the matter–I’m open to correction. Aquinas didn’t think that will and intellect were cordoned off from each other–he thought that if you choose to focus on something you can influence your intellect, even though the intellect is primarily the guiding partner in the relationship.
I think this is basically compatible with William James’s account in *The Will to Believe *(which builds to some extent on “Pascal’s Wager”). James points out that choosing not to commit yourself to a belief is just as much of a choice as choosing to commit yourself. So since you have to do one or the other, there is nothing dishonest about choosing to believe even if the evidence is not entirely conclusive.
The difference between this kind of “agnosticism” and classical agnosticism as defined by T. H. Huxley is that Huxley insisted that it is wicked and dishonest to commit yourself to anything that has not been proven to be true. I think James’ critique is valid–if followed consistently, this leaves one paralysed on most important questions of life.
Since Huxley invented the term “agnosticism,” it is perhaps discourteous to hijack it for a quite different point of view. I have sometimes called myself a “believing agnostic,” but mostly for shock value. At any rate, I cannot imagine being without doubts on any matter that is really important. This is the way I am, and I have to make the most of it. In fact it’s a struggle for me not to look down on people who find believing easy. It’s hard for me to see how they could really be taking the issues seriously. But what do I know? Maybe they just have a more direct line to God than I do. Or at least some of them do.