The core idea a story sets out to dramatize - the 'what if' and the argument it puts to the test.
A premise is the seed statement of a story: the 'what if' that generates the plot, sometimes phrased as a proposition the story will prove or disprove ('great ambition destroys the ambitious'). It's broader than a logline and more foundational - the belief the whole draft exists to argue.
A muddy premise shows up everywhere downstream as scenes that don't seem to be about anything. Nailing it early gives every later choice a test to pass: does this scene advance the argument, or is it just event? The premise is where structure and theme first meet.
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