The topic of certainty is a difficult one. Certainty can be viewed as a psychological state. We say, ‘I am certain that he was killed in the war’, and this reflects the degree of assurance we possess about some state of affairs. I don’t have a problem with this kind of certainty. I am certain, and I feel certain, about all sorts of matters: I am certain that I live in Australia, I am certain that there are no elephants in my office, and so on. But the kind of certainty I was concerned with in my article was not this psychological kind of certainty, but the more philosophical kind, as when we say that such-and-such doctrines are not merely possibly true or probably true, but are certainly true: there are absolutely no grounds whatsoever for doubting them. The problem with this kind of certainty is that there will always be at least some grounds for doubting the truth of some doctrine or teaching. In any case, (philosophical) certainty or infallible knowledge is not necessary for faith – that would be asking for the impossible.
I would like to add, however, that I now see things a little differently. How we approach these kinds of questions will depend largely on how we think of religious doctrines and teachings. Are doctrines to be thought of as philosophical theories that are open to empirical confirmation and speculative doubt? Or are doctrines to be thought of as guides or pointers as to how to live and love? I am beginning to favor the second option.
Also, I never argued that there are no precise set of criteria for infallibility. Rather, I argued that these criteria could not, in practice, be fulfilled.