Proveability

"Though the worship of Sun-gods and divine figures in the sky came comparatively late in religious evolution, I have put this subject early in the book (chapters ii and iii), partly because (as I have already explained) it was the phase first studied in modern times, and therefore is the one most familiar to present-day readers, and partly because its astronomical data give great definiteness and "proveability" to it, in rebuttal to the common accusation that the whole study of religious origins is too vague and uncertain to have much value."