But a science is exact to the extent that its method measures up to and is adequate to its object.

Metaphysics is a science.

With all the measures we have taken and all measures we propose, most likely we have adequate measures and the H5N1 virus only has limited transmission to poultry and to humans.

Politics is not an exact science.

The whole [scientific] process resembles biological evolution. A problem is like an ecological niche, and a theory is like a gene or a species which is being tested for viability in that niche.

Not that the incredulous person doesn't believe in anything. It's just that he doesn't believe in everything. Or he believes in one thing at a time. He believes a second thing only if it somehow follows from the first thing. He is nearsighted and methodical, avoiding wide horizons. If two things don't fit, but you believe both of them, thinking that somewhere, hidden, there must be a third thing that connects them, that's credulity.