One can be all there is, the first of all the ones that come, the one all this time you knew was right.
One can be too much to handle or not enough if you are greedy, and not for you if you are needy. With the power out, one candle may not be enough to light the house.
But one little shining star along the mass of grey, or green in war with black, can be enough to brighten up the park at night. One light to make the road less scary.