for all someone knows

for all (one) knows

Said when one is uncertain or has limited details about something. I haven't talked to Marie in weeks, so, for all I know, she's not even coming to the dinner party tonight.
See also: all, know

for all someone knows

COMMON You use for all someone knows to say that person does not know the facts of a situation. For all we know, he may even not be in this country. She's had a miserable time staying faithful to someone who for all she knows might not be coming back.
See also: all, know, someone

for all someone knows

used to express the limited scope or extent of someone's information.
See also: all, know, someone