If there are—if, for instance, there are possible but non-actual dogs (dogs of some non-actual but possible species, perhaps) or nonexistent beings (like Sherlock Holmes, perhaps)—then these things might also figure in the extensions of various concepts and expressions.
如果有--就是说有着可能的但不真实的狗（某些不真实但可能的种类的狗），或不存在的人（比如福尔摩斯），那么这些事物也可以在在各种概念和表达的外延中出现。