The president has a vacancy to fill on the Supreme Court. The
president appoints a justice, but that
justice does not become a member
of the Supreme Court. How is this
possible?

It is possible because the body that actually approves or rejects the appointment of a candidate to Supreme Court Justice is the Senate.

The president selects a candidate who meets the criteria to become justice, and the Senate has to vote on whether to approve or reject the candidate. The candidate can become justice simply by winning a plurality of votes in the Senate, that is to say, at least 51 votes.

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answer; collective security;