[annalex]

If we don't know when the magesterium was created or how bishops are selected

We know both things very well. The Magisterium is a way to describe the bishops of the Church as the same body. It was created at the same time the Church was created, at Pentacost. The selection of bishops is the subject of the epistles to Titus and Timothy: men of good character and education show themselves worthy of the job and receive the call of the Holy Spirit, and someone with authority consecrates them.

[wmfights]

"The Magisterium is a way to describe the bishops of the Church as the same body."
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Okay, so every bishop is a member of the magesterium?

Do they meet to resolve questions whenever they arise? If so is it a conclave at the Vatican, or some other location?