Joshua means Jehovah saves, and he is the power in you that carries out the promise, your own imagination bringing you into what you long for. Jericho is not a walled town but the most desirable state you could occupy, the fulfilled wish waiting to be entered. The spy sent secretly is imagination itself, which can travel into that state unseen by anyone around you and take up residence there before a single fact has changed.
Rahab, whose house the spy enters, is the spirit of the Father in you, your own awareness of being, your I AM. So the movement here is quiet and inward: your attention slips out of the life you are living, walks over into the state you want as though it were already so, and lodges there. Whatever state you can occupy in your mind becomes yours in fact. You dwell in the wish fulfilled, unobserved, and it hardens into reality.