ray of light

noun

a) a path a photon or a group of photons takes through space, visible as a column of light

I think he was somewhat lost for a political position - a simple conservatism did not attract him - and I make the guess that Arnold had been a spar that he got hold of as he struggled to find a political position. I was certainly in that position, having been persuaded by Anderson, especially at the lunch-hour meetings of his Free-thought Society, of the bankruptcy of the Left. Arnold came to me as a most welcome ray of light.

b) an inspiring or enlightening person or thing