Final answer:
Weiss's theory is not confirmed to have arisen from seminars for widows and those recently separated. The theory might involve aspects of social isolation or activities following major life changes, which is suggested by the scenarios described.
Step-by-step explanation:
The question deals with Weiss's theory, which is not directly associated with his work with seminars for widows and those recently separated. Instead, Weiss's theory likely refers to a sociological concept that may have emerged from research in social behavior or psychological studies that are not detailed in the information provided. From the context clues given, it seems that Weiss's theory could be related to social isolation or activity after significant life changes such as retirement or losing a spouse, but without more specific information, it's difficult to confirm the exact nature of Weiss's theory. Furthermore, the examples from the provided information, such as the older man who isolates himself after his wife dies or the older woman who remains active by joining different community groups, hint at broader social theories dealing with isolation, engagement, and societal roles.