Although science does not provide proofs, it does provide explanations. Science depends on deliberate, explicit and formal testing (in the natural world) of explanations for the way the world is, for the processes that led to its present state, and for its possible future. When scientists see that a proposed explanation has been well confirmed by repeated observations, it serves the scientific community as a reliable theory. A theory in science is the highest form of scientific explanation, not just a “mere opinion.” Strong theories, ones that have been well confirmed by evidence from nature, are an essential goal of science. Well-supported theories guide future efforts to solve other questions about the natural world.