A man's knowledge may be said ...

A man\'s knowledge may be said to be mature, in other words, when it has reached the most complete state of perfection to which he, as an individual, is capable of bringing it, when an exact correspondence is established between the whole of his abstract ideas and the things he has actually perceived for himself. His will mean that each of his abstract ideas rests, directly or indirectly, upon a basis of observation, which alone endows it with any real value; and also that he is able to place every observation he makes under the right abstract idea which belongs to it.
A man's knowledge may be said to be mature, in other words, when it has reached the most complete state of perfection to which he, as an individual, is capable of bringing it, when an exact correspondence is established between the whole of his abstract ideas and the things he has actually perceived for himself. His will mean that each of his abstract ideas rests, directly or indirectly, upon a basis of observation, which alone endows it with any real value; and also that he is able to place every observation he makes under the right abstract idea which belongs to it.
 Arthur Schopenhauer

Quotes from the same author

Every man takes the limits of his own field of vision for the limits of the world.
 See image
 Arthur Schopenhauer
In action a great heart is the chief qualification. In work, a great head.
 See image
 Arthur Schopenhauer
If children were brought into the world by an act of pure reason alone, would the human race continue to exist? Would not a man rather have so much sympathy with the coming generation as to spare it the burden of existence, or at any rate not take it upon himself to impose that burden upon it in cold blood?
 See image
 Arthur Schopenhauer
A man of business will often deceive you without the slightest scruple, but he will absolutely refuse to commit a theft.
 See image
 Arthur Schopenhauer
The first forty years of life give us the text; the next thirty supply the commentary on it.
 See image
 Arthur Schopenhauer