When someone is "past caring", it means that they are no longer interested or concerned about a particular situation or issue. This expression can have negative connotations, indicating a feeling of hopelessness or apathy. Some synonyms for "be past caring" include "be indifferent", "be unconcerned", "not give a damn", "not care a jot", and "be apathetic". Other similar phrases may include "be resigned to", "give up", or "throw in the towel". These terms all convey a sense of disengagement or detachment, suggesting that the person has lost interest or has become disillusioned with a situation they previously cared about.