There's a great essay by Schopenhauer called "On Thinking for Yourself" which deals with this and related themes. I'll post it here for your benefit (from the great Penguin translation titled "Essays and Aphorisms":

On Thinking for Yourself

1--
As the biggest library if it is in disorder is not as useful as a small but well-arranged one, so you may accumulate a vast amount of knowledge but it will be of far less value to you than a much smaller amount if you have not thought it over for yourself; because only through ordering what you know by comparing every truth with every other truth can you take complete possession of your knowledge and get it into your power. You can think about only what you know, so you ought to learn something; on the other hand, you can know only what you have thought about.
Now you can apply yourself voluntarily to reading and learning, but you cannot really apply yourself to thinking: thinking has to be kindled, as a fire is by a draught, and kept going by some kind of interest in its object, which may be an objective interest or merely a subjective one. The latter is possible only with things that affect us personally, the former only to those heads who think by nature, to whom thinking is as natural as breathing, and these are very rare. That is why most scholars do so little of it.

2--

The difference between the effect produced on the mind by thinking for yourself and that produced by reading is incredibly great, so that the original difference which made one head decide for thinking and another for reading is continually increased. For reading forcibly imposes on the mind thoughts that are as foreign to its mood and direction at the moment of reading as the signet is to the wax upon which it impresses its seal. The mind is totally subjected to an external compulsion to think this or that for which it has no inclination and is not in the mood. On the other hand, when it is thinking for itself it is following its own inclination, as this has been more closely determined either by its immediate surroundings or by some recollection or other: for its visible surroundings do not impose some single thought on the mind, as reading does; they merely provide it with occasion and matter for thinking the thoughts appropriate to its nature and present mood. The result is that much reading robs the mind of all elasticity, as the continual pressure of a weight does a spring, and that the surest way of never having any thoughts of your own is to pick up a book every time you have a free moment. The practice of doing this is the reason erudition makes most men duller and sillier than they are by nature and robs their writings of all effectiveness: they are in Pope’s words:
For ever reading, never to be read.

3--
Fundamentally it is only our own basic thoughts that possess truth and life, for only these do we really understand through and through. The thoughts of another that we have read are crumbs from another’s table, the cast-off clothes of an unfamiliar guest.

4--
Reading is merely a surrogate for thinking for yourself; it means letting someone else direct your thoughts. Many books, moreover, serve merely to show how many ways there are of being wrong, and how far astray you yourself would go if you followed their guidance. – You should read only when your own thoughts dry up, which will of course happen frequently enough even to the best heads; but to banish your own thoughts so as to take up a book is a sin against the Holy Ghost; it is like deserting untrammelled nature to look at a herbarium or engravings of landscapes.
It may sometimes happen that a truth, an insight, which you have slowly and laboriously puzzled out by thinking for yourself could easily have been found already written in a book; but it is a hundred times more valuable if you have arrived at it by thinking for yourself. For only then will it enter your thought-system as an integral part and living member, be perfectly and firmly consistent with it and in accord with all its other consequences and conclusions, bear the hue, colour and stamp of your whole manner of thinking, and have arrived at just the moment it was needed; thus it will stay firmly and for ever lodged in your mind. This is a perfect application, indeed explanation, of Goethe’s lines:
Was du ererbt von deinen Vätern hast,
Erwirb es, um es zu besitzen.*

For the man who thinks for himself becomes acquainted with the authorities for his opinions only after he has acquired them and merely as a confirmation of them, while the book-philosopher starts with his authorities, in that he constructs his opinions by collecting together the opinions of others: his mind then compares with that of the former as an automaton compares with a living man.
A truth that has merely been learnt adheres to us only as an artificial limb, a false tooth, a wax nose does, or at most like transplanted skin; but a truth won by thinking for ourself is like a natural limb: it alone really belongs to us. This is what determines the difference between a thinker and a mere scholar.

5--
People who pass their lives in reading and acquire their wisdom from books are like those who learn about a country from travel descriptions: they can impart information about a great number of things, but at bottom they possess no connected, clear, thorough knowledge of what the country is like. On the other hand, people who pass their lives in thinking are like those who have visited the country themselves: they alone are really familiar with it, possess connected knowledge of it and are truly at home in it.

ctd...