Excerpt from The Art of Worldly Wisdom by Baltasar Gracián.

clxxvi Have Knowledge, or know those that have Knowledge.

Without intelligence, either one's own or another's, true life is impossible. But many do not know that they do not know, and many think they know when they know nothing. Failings of the intelligence are incorrigible, since those who do not know, do not know themselves, and cannot therefore seek what they lack. Many would be wise if they did not think themselves wise. Thus it happens that though the oracles of wisdom are rare, they are rarely used. To seek advice does not lessen greatness or argue incapacity. On the contrary, to ask advice proves you well advised. Take counsel with reason if you do not wish to court defeat.