“The purpose of life is unquestionably unfoldment, growth, advancement”
Trine states his view of purpose directly: life should continue to develop rather than settle into mental or moral stagnation.
Source details
The Higher Powers of Mind and Spirit; Project Gutenberg #28163. The surrounding text describes evolution from “lower” to “higher” in spiritual terms; this is Trine’s philosophical-religious position, not a scientific law of human development.