What can justify the scientists’ faith that there is no event without a cause or at least without a good explanation? What can justify the faith that the laws of nature will operate in the future as they have in the past? What can justify the belief that human reason is adequate to understand the structure of reality? As the Cambridge quantum physicist Paul Dirac said, “It was a sort of act of faith with us that any equations which describe fundamental laws of Nature must have great mathematical beauty in them” (quoted in Longair 1984, 7).
This is the same tired-ass comparison of science to religion that has been around for decades, if not centuries. Seriously, he's asking what the justification for causality in the universe is? How about virtually every moment of waking life and every experiment ever carried out. We have overwhelming evidence that when we take our next step on a sidewalk we will not plunge through to the center of the earth. This is NOT faith. It is a belief borne out from extensive prior evidence.
Same with how we can work under the assumption that the laws of nature will act in the future as they did in the past. We can't know this with 100% certainty, but it is a strongly-justified belief based on prior evidence and experience. And again, we don't know that the human intellect will be sufficient to understand every intricacy of the universe, but we seem to be making good progress, and we should continue until we hit that wall, don't you think?
He then goes on at length about history and art, noting that both contain truth, but not the kind that is accessible by scientific methods. All right...I'd concede that point. I'd also concede the larger point that the truth is not always accessible to the scientific method per se. That doesn't mean that we abandon reason and standards of evidence. He takes the example of whether or not Caesar crossed the Rubicon. How do we decide whether to believe this is the case or not? Well, one perspective would be to say there's no real way of getting at the truth...that different people will have different perspectives, so I'll just believe whatever satisfies my personal tendencies. Or...we could ask what evidence there is that Caesar crossed the Rubicon and assess how reliable that evidence is. If the evidence is strong in either direction, we can make a judgment. If it's vague or incomplete, we'll have to be content to say we just don't know whether Caesar crossed the Rubicon.
His basic strategy is to try to lower the bar for what we should believe. See, he says, there are all sorts of things that we believe that science can't verify, so it's open season on believing without strong evidentiary standards. The problem with this kind of thinking is pretty clear. Once you lower the bar this far, anything goes. According to this way of thinking, belief in ghosts, witches, leprechauns, dragons, faeries, Santa Claus, Bigfoot, and on and on is just as valid as belief that the earth revolves around the sun. Basically, if you don't have any standards for belief, you can justify belief in anything. And that's not a very sensible position, is it?