 Indeed, it is even arguable that some marks of intensionality are present with verbs that allow interchange of accidentally co-extensive expressions. A case in point is verbs of absence, such as ‘omit’ and ‘lack’. If it so happens that all and only the physicists on the faculty are the faculty’s Nobel prize winners, then a faculty committee that lacks a physicist lacks a Nobel prize winner. However, not too much weight can be put on this case, since it may be that at some level, ‘lack’ should be analyzed (possibly in a complicated way) in terms of not having, in which case it would not really be an intensional verb at all; though so far as the author knows, no convincing analysis of this type has been formulated. See (Zimmerman 2001, 516–20) for further discussion of relationships among the marks of intensionality.