Final answer:
Deviation from social norms as a definition of abnormality is subjective and varies culturally, making it unreliable and not universally valid.
Step-by-step explanation:
Two weaknesses of deviation from social norms as a definition of abnormality are subjectivity and cultural variability. Subjectivity refers to the fact that what is considered normal behavior is often based on individual perspectives, which can vary greatly from person to person. Cultural variability highlights that norms differ widely among various cultures, and what is deemed abnormal in one society may be perfectly normal in another. As a result, using deviation from social norms to define abnormal behavior might not consistently reflect psychological abnormality due to these inherent limitations, questioning the reliability and validity of such a definition across different contexts.