A combination of pragmatism and hubris. pragmatism: our best current theories about the universe suggest that the speed of light is a constant. Until someone p

A combination of pragmatism and hubris. pragmatism: our best current theories about the universe suggest that the speed of light is a constant. Until someone proposes a theory with more explanatory power that suggests otherwise, we might as well do our work with the assumption that it's correct. Hubris: our best theories are clearly not complete (see dark matter, conflicts between general relativity and quantum mechanics, and similar), yet we mostly treat them not as provisional theories subject to change, but as ironclad laws by which we may live our lives. Humans don't do well with uncertainty. (Disclaimer: not everyone lives that way. As far as I can tell most who do have something like this combination of ideas in their heads.)