I am a beacon, to warn you from the danger of setting up false beacons to mislead you

I am a beacon, to warn you from the danger of setting up false beacons to mislead you. I am a buoy, to point out to you the way in which you ought to mark out beacons to direct other people. I am a light, to show you how to make a proper use of beacons and buoys, so as to prevent them from being abused. I am a mark, to let you know, that, in order to avoid confusion, be