Final answer:
The theory of evolution is a well-supported and foundational scientific explanation for the diversity of life, subject to rigorous testing and not just an unsupported guess. The scientific usage of the term 'theory' differs greatly from the common everyday usage, lending significant credibility to evolutionary theory.
Step-by-step explanation:
The theory of evolution is a foundational scientific explanation that describes the mechanisms by which species change over time. In science, the term theory refers to a body of thoroughly tested and verified explanations, not just a simple guess as often misconstrued in everyday language. Evolutionary theory is as factual and substantiated as other scientific theories like the atomic theory of matter or the germ theory of disease. As with all scientific theories, it is subject to continued testing and revision, but this is a rigorous process that only strengthens the body of evidence supporting the theory. Therefore, the assertion that evolution is just a 'theory' in the sense of being an unsupported guess is a significant misinterpretation of the scientific meaning of a theory.
The theory of evolution has undergone extensive scrutiny and has been supported by a multitude of observations and experimental evidence, which makes it a reliable account of the natural world and not merely a 'just a theory.' The misconception that evolution is widely debated or controversial among scientists is incorrect, as the majority of the scientific community accepts evolution as the unifying theory of biology. Evolution provides the explanatory framework within which biologists approach all questions about the living world, and its understanding continues to evolve and refine as new evidence emerges.