The only means of strengthening one's intellect is to make up one's mind about nothing --to let the mind be a thoroughfare for all thoughts. Not a select party.
Source: Letter, 17-27 Sep 1819, in Letters of John Keats, no. 90, ed. by Frederick Page, 1954.
-- John Keats, (Oct 31 1795-1821), English poet; He was one of the foremost Romantic poets whose poems included Ode on a Grecian Urn.