The following are excerpts from an essay written by Arthur Schopenhauer in 1851 and translated into English by L.P. Koch. The full essay is available here.

Excerpt 1:
Reading, you see, forces thoughts on your mind that are as foreign and incompatible with its current direction and mood as the signet is to the wax on which it impresses its seal. Which means that during reading, the mind has to suffer the utter external coercion to think now this, now that, even while at the moment it might neither have the drive nor be in the mood for it. – When thinking for yourself, on the other hand, your mind follows its very own drive, as triggered and shaped either by your current surrounding or some memory. This is because your palpable surrounding, unlike reading, doesn’t impose one particular thought on the mind, but merely provides it with the raw material and stimulation to think something according to its own nature and current disposition. – Hence reading a lot robs the mind of all elasticity, just as the constant pressure of a weight takes it from the spring. This is the reason why scholarly erudition impoverishes most people’s spirits even more, and makes them even stupider than they already are by their very nature.

Excerpt 2:
As with people, so with thoughts: you can’t always call them up when you want to, but must rather wait patiently until they arrive. Thinking about a certain matter must present itself to you on its own terms by way of a fortunate, harmonious coming together of the external trigger and the right inner atmosphere and tension. . . . That being said, even the greatest mind is not able to think for himself all the time. Thus he would be well-advised to use the remaining time to read, even though as I said it is a surrogate for thinking for oneself. . . . Least of all should you give up looking at the real world in favour of reading: because it is there that the occasion and the atmosphere for thinking for yourself will knock at your door much more often than by reading. For it is the vivid, the exemplification, the real, in its primal power, which is the natural matter of the thinking mind, and can stir it deeply most reliably.

Excerpt 3:
If we consider in earnest how great and obvious the problem of Being truly is, this ambiguous, tortured, ephemeral, dream-like Being; a problem so great and obvious that it overshadows and dwarfs all other problems or goals the minute one becomes aware of it; and if we further bring to mind how all people, except the very rare and few, are not aware of this problem in any clear way, or worse, don’t even know it exists, but rather put all their effort into anything and everything; wasting away their life, their minds set exclusively on the current day and the hardly longer time span of their personal future. . . . we may well come to the conclusion that we should call man a thinking being only in a very loose sense indeed.