The intellect is never in every respect what it possibly might be.
 Arthur Schopenhauer, The World as Will and Representation (1819). copy citation

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Author Arthur Schopenhauer
Source The World as Will and Representation
Topic respect intellect
Date 1819
Language English
Reference
Note Translated by R. B. Haldane and J. Kemp
Weblink http://www.gutenberg.org/files/40097/40097-h/40097-h.html

Context

“But even after it has ascended through the whole series of animals to man and his reason, the unconsciousness of plants, from which it started, still remains the foundation, and may be traced in the necessity for sleep, and also in all those essential and great imperfections, here set forth, of every intellect produced through physiological functions; and of another intellect we have no conception. The imperfections here proved to be essential to the intellect are constantly increased, however, in particular cases, by non-essential imperfections. The intellect is never in every respect what it possibly might be. The perfections possible to it are so opposed that they exclude each other. Therefore no man can be at once Plato and Aristotle, or Shakspeare and Newton, or Kant and Goethe. The imperfections of the intellect, on the contrary, consort very well together;” source