The property of optical activity—where chiral media rotate plane-polarized light due to differing refractive indices for left- and right-circularly polarized components (circular birefringence)—is a foundational, textbook principle of physical chemistry and optics requiring no further citation.
The claim states the fundamental physical definition of optical activity (circular birefringence), which is universally established in physics and chemistry by definition and direct observation. Step 0 dictates classifying such basic definitions as common knowledge without needing citations.