“Of Optimism I have said that "The world is the best of all possible worlds, and everything in it is a necessary evil."”
Appearance and Reality, preface http://books.google.com/books?id=EtgtAAAAYAAJ&q=%22of+optimism+I+have+said+that+The+world+is+the+best+of+all+possible+worlds+and+everything+in+it+is+a+necessary+evil%22&pg=PR14#v=onepage (1893).
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F. H. Bradley 19
British philosopher 1846–1924Related quotes

“The Optimist thinks this is the best of all possible worlds, the Pessimist fears it is true.”
This is derived from a statement of James Branch Cabell, in The Silver Stallion (1926) : The optimist proclaims that we live in the best of all possible worlds; and the pessimist fears this is true.
Misattributed
Variant: The optimist thinks this is the best of all possible worlds. The pessimist fears it is true.

“In my world, everything is possible and everything is relative.”
Source: The Zahir (2005), p. 167.

“Premature optimization is the root of all evil.”
Quote due to Donald Knuth, "Structured Programming with Goto Statements" http://pplab.snu.ac.kr/courses/adv_pl05/papers/p261-knuth.pdf, Computing Surveys 6:4 (December 1974), pp. 261–301, §1. Knuth refers to it as "Hoare's Dictum" 15 years later in "The Errors of TeX", Software—Practice & Experience 19:7 (July 1989), pp. 607–685. However, the attribution to Hoare is doubtful. http://shreevatsa.wordpress.com/2008/05/16/premature-optimization-is-the-root-of-all-evil/
Attributed
Source: Ideas Have Consequences

“If this is the best of possible worlds, what then are the others?”
Citas, Candide (1759)

This is actually James Branch Cabell from The Silver Stallion (1926)
Misattributed