alternative theory — a theory that provides a different explanation or approach from the mainstream or accepted theory

a younger professor points enthusiastically at a large chalkboard showing a completely different diagram than the traditional one displayed next to it. Her passionate gestures contrast sharply with the established model that everyone usually accepts. The older professor beside her looks skeptical while holding up the conventional textbook explanation. Students in the audience lean forward with mixed expressions of curiosity and confusion as they compare the two opposing explanations. Some students nod thoughtfully while others whisper among themselves about this new perspective. a theory that provides a different explanation or approach from the mainstream or accepted theory