But. Marking the contrast between the growth of wickedness (verses: Pro_4:16, Pro_4:17), and the growth of wisdom leading in right paths (verses: Pro_4:11, Pro_4:12).
the shining light = the dawning of day: advancing and brightening till noon.
perfect = stable part, when the sun seems stationary on the meridian. Illustrations: Jacob (Gen_49:10, Gen_49:18. Heb_11:21); Nathanael (Joh_1:46-51); Eunuch (Act_8:27-39).