“Our intellectual and active powers increase with our affection.”
Affection can call forth capacities that remain dormant in isolation; Emerson illustrates the claim with a writer who suddenly finds thoughts and words when writing to a friend.
Source details
Essays: First Series, “Friendship” (1841), verified against Project Gutenberg #2944 and the page-numbered 1907 Merrill/Turpin Essays witness in Project Gutenberg #16643, printed page 117. Emerson says “Our intellectual and active powers increase with our affection” before illustrating the claim with a scholar who finds thoughts and language when writing to a friend; it remains literary-philosophical observation rather than a quantified psychological law.