Active scientists do not run around declaring that science can explain everything. For example, no one of us claims that science can explain love or hate or beauty or valor or cowardice. But as science advances, these notions may indeed come into the experimental purview of science, just as so many previously intractable subjects have done in the past. This is not an absolute faith as you describe it, it is a prevailing confidence based on past performance of the methods and tools of science.
