Furthermore, in addition to being unreliable by dint of leading to mutually contradictory "truths," conclusions drawn from faith are also unreliable in ascertaining raw data about the universe. As the Professor noted, you can simply study the real world impact of various claims, and they simply do not match what faith dictates should happen. We have a lot of instances of people making claims that should affect the real world, whether it be faith healers, intercessory prayer, divination, etc. When actually tested, there has not been a single instance in which a supernatural claim has been shown to have merit.
So, we have two points of data:
- Faith leads to contradictory conclusions, and is thus unreliable.
- Faith leads to conclusions about the natural world which are testable and are demonstrably false, and is thus unreliable.
- Faith in general might be unreliable, but a particular faith might be reliable.
- Faith might be unreliable for empirical conclusions, but might be reliable for conclusions about supernatural events or properties.
The problem with the second is that it is, in effect, begging the question. You have to first have faith that the supernatural exists, itself a matter of faith, before you can say that faith X is capable of explaining it. This is the equivalent of saying that my theory of snurk-hurdling is true because it alone explains the existence and nature of snurks. For a more "real world" example, look at the concept of canon in constructs such as Star Wars and/or Star Trek. There are elaborate arguments made about which bits are true, which are not and what conclusions can be drawn from those accumulated bodies of knowledge. The fact that the canons are(or can be) cohesive has no bearing on the fact that they are fictional accounts. The same goes for "faith claims." The fact that a faith claim may explain something about the nature of heaven is useless without first establishing the existence of said heaven. If all you are left with is a self-referential piece of dogma, then the best you can do is chase your own tail.
About the only quibble I have with the talk is that he included transubstantiation as an example of a claim that can be empirically disproven. Being familiar with Catholic theology, I can tell him that the Catholic theologians would immediately retreat to talking about "accidents" and "substance." In effect, the "substance" of the original materials, bread and wine, are transformed into Jesus, while the "accidents," the way that our senses perceive those materials, stays the same. Of course, this is an obvious cop out. It's just a dodge to avoid the obvious conclusion that transubstantiation is false by simply noting that there is no empirical change happening to the bread and wine.