It is hard to talk about a “chair” if nobody agrees on what a chair is. There is enough of a common example base in OO, the shape, animal, and device-driver examples; that one can start, but beyond that the nature of OO diverges from person to person.
I’ll take that challenge. Find a definition of chair. For any said definition of finite length, their is either an exception to the definition or a thing that is a chair that isn’t covered by the definition. And yet, we can still talk about chairs.[A lot of this is because OO is a broad church embracing everyone from the prototype-based (Self, Io, JavaScript) to the class-based (Java, SmallTalk, etc ) to those who have built OO systems on top of other paradigms (CLOS, OCaml, various Scheme dialects, Python, Perl). Each of these have various flavors of usage as well so talking about OO without qualifying it usually becomes a meaningless debate about whose definition we shall use.
We can only talk about chairs if we first state that we’re only interested in wooden 4-legged chairs.]
I suppose we have beanbag chairs that are borderline “mini-couches”. But, this gets back to the need for a working classification system for OO. I don’t know if “modeling” can be separated from language or not.