An open mind is not one that believes everything; it is one willing to examine anything.

Openness is not credulity. Believing everything is just a different way of not thinking, and it is often mistaken for the open-minded position. The real version is a willingness to examine a claim on its merits, which includes the willingness to conclude that it is wrong.

In practice, try separating consideration from acceptance. Give an unfamiliar idea a genuine hearing, look at what would have to be true for it to hold, and then judge it. That combination lets you take in new things without being moved by every confident voice that reaches you.