guiding star (?.)

• North Star
• Polaris
• ambition
• aspiration
• basis
• calling
• cause
• consideration
• cynosure
• goal
• ground
• guiding light
• ideal
• inspiration
• intention
• lodestar
• mainspring
• matter
• motive
• polar star
• polestar
• principle
• reason
• sake
• score
• source
• spring
• ulterior motive
• vocation