have/keep an open mind

have an open mind

To avoid making a judgment or decision about someone or something without full knowledge. I know you think that Morton is a dullard, but try to have an open mind—once you get to know him better, you'll find that he's really quite funny.
See also: have, mind, open

keep an open mind

To avoid making a judgment or decision about someone or something without full knowledge about them or it. I know you think that Morton is a dullard, but try to keep an open mind—once you get to know him better, you'll find that he's really quite funny. I don't usually like musicals, but I'm keeping an open mind.
See also: keep, mind, open

have/keep an ˌopen ˈmind (on/about something)

be willing to change your opinion (on/about something): I’ve still got an open mind on the question of nuclear defence. ▶ ˌopen-ˈminded adj.: You can talk to her about anything — she’s very open-minded.
See also: have, keep, mind, open