What is determined?

I recently came across this book description:

In If Not God, Then What? theoretical neuroscientist Joshua Fost shows how the search for beauty is the source of both religious experience and scientific theorizing. The pleasure of seeing a beautiful face, the thrill of understanding a new idea, the sublimity of art and the power of religious transformation are all, in the end, the result of a brain that wants to make sense of the world. Weaving ideas from brain science and everyday activities, from Sunday cartoons to existentialism, Fost shows how a biological idiosyncrasy motivates them all. But if religious experience is just a special activity pattern in neurons, what should we think about its undeniable and emotionally transformative power? If everything we do is determined by physics, what is the basis for free will, or ethics? Blending receptivity to the glory of spiritual exultation with an insistence on naturalistic foundations, If Not God, Then What? breaks new ground and gives its readers insight into a compelling new worldview.

The phrase I found most troubling is "If everything we do is determined by physics..." - this just seems wrong to me as a proposition.  The laws of physics constrain what is possible, but they do not seem to determine or predict what is possible.  Do the laws of physics determine that the boiling point of water is at 100 Centrigrade? I don't think so.  In fact we don't know very much about the actual properties of substances until we experiment.

Likewise, computers are constrained by operating on particular chips.  Does this mean that we can predict everything that is possible to do with computers? 

And our brains operate with neurons and bio-chemical reactions, etc.  Does this mean that we can predict all that is possible with our minds?  I think not.  We need to experiment to see what is possible.