A premise answers the question: Why believe this?
It provides the reasoning or evidence that supports the main claim. Here's a breakdown of your questions:
What else is true? This questions asks for the implications of the main claim. It explores the consequences or logical outcomes that follow from accepting it as true.
Why believe this? This questions seeks the justification of the main claim. It asks for the reasons, evidence, or arguments that support it.
What’s a premise? This question directly asks for the definition of a premise. A premise is a proposition or statement that serves as the basis for an argument and supports the main claim.
Therefore, Why believe this?, is directly answered by a premise.