The Fifth Theosophical Ray is the Ray concerned with the accuracy of observation, so with science. Controlling it is the entity Mahachohn who it seems has authority like a Prime Minister over the Third to Seventh Rays since they each affect in some way the mind, bliss or activity. The Masters of these Rays are similar to ministers of his Cabinet. The Master guiding it is Hilarion, a Neo-Platonist. It provides the path for those whom science leads to the ultimate truth. A.G.H.
Ellwood, Robert. Theosophy: A modern expression of the wisdom of the ages. Wheaton, IL. Quest Books. 1994. pp. 142