“But that disease when soberly defined
Is the false fire of an o'erheated mind.”
Source: Conversation (1782), Line 667; of fanaticism.
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William Cowper 174
(1731–1800) English poet and hymnodist 1731–1800Related quotes

“When beauty fires the blood, how love exalts the mind!”
Source: Fables, Ancient and Modern (1700), Cymon and Iphigenia, Line 41.

Edward Young, "Night Thoughts," (1742-1745) Part IX http://www.litgothic.com/Texts/young_night_thoughts.pdf.
Misattributed

“Diseases of the mind are more common and more pernicious than diseases of the body.”
Morbi perniciosiores pluresque sunt animi quam corporis.
Book III, Chapter III
Tusculanae Disputationes – Tusculan Disputations (45 BC)

“Words are the physicians of a mind diseased.”
Source: Prometheus Bound, line 378; compare: "Apt words have power to suage / The tumours of a troubl'd mind", John Milton, Samson Agonistes.
Rowe, John W., and Robert L. Kahn. " Successful aging http://gerontologist.oxfordjournals.org/content/37/4/433.full.pdf." The gerontologist 37.4 (1997): 433-440.

"When I Think Of My People Broken Down", as translated in "The Poetry of Sri Lanka", in Journal of South Asian Literature, Vol. 12, No. 1 (Fall-Winter 1976), published by Asian Studies Center, Michigan State University, p. 11
Context: Unbearable becomes the pain in my heart —
When I think of my people, broken down,
broken by disease in mind and limb. On the edge of life they always linger;
For countless are the diseases
Of Ignorance and Hunger. And on treacherous paths to Slavery
like children blind, they would walk behind
strangers from over the sea. O, divine Land, blessed by the gods!
O, ancient Mother of Culture and Art!
Thy children today are spineless hordes.

“The confusion of mind you dub honor is a disease.”
Source: World of the Five Gods series, The Curse of Chalion (2000), p. 282
“Melancholy
Is not, as you conceive, indisposition
Of body, but the mind's disease.”
Act III, sc. i.
The Lover's Melancholy (1628)