He was not so frugal in his optics. To account for partial reflection and interference he posited that at least at critical moments each photon is controlled by otherwise invisible waves that accompany all photons everywhere. People call such hypothetical waves guide wave or pilot waves today. For Newton, the interference of light was a by-product of the interference of guide waves, and the photons themselves had no intrinsic wave character. Presumably the occupants of space are the thoughts of this central nervous system.
Guide waves are transverse ether waves.
Einstein's theory of relativity is sometimes thought to eliminate the ether from physics. It would not have done so for Newton, who needed the ether to account for quantum interference, not propagation. To constitute the ether Newton inferred still other particles besides photons. Ether waves have to go as fast as light in order to guide light, and since a density wave in a medium travels substantially slower than the atoms of the medium, Newton knew that his etherons must travel faster than light. The quantum theory obviates Newton's tachyons and hot tachyonic crystalline ether.