John Locke said this quote

For where is the man that has incontestable evidence of the truth of all that he holds, or of the falsehood of all he condemns; or can say that he has examined to the bottom all his own, or other men's opinions? The necessity of believing without knowledge, nay often upon very slight grounds, in this fleeting state of action and blindness we are in, should make us more busy and careful to inform ourselves than constrain others.

~ John Locke

The only defense against the world is a thorough knowledge of it.

~ John Locke

...but since He gave it them for their benefit and the greatest conveniences of life they were capable to draw form it, it cannot be supposed He meant it should always remain common and uncultivated. He gave it to the use of the industrious and rational (and labour was to be his title to it)...

~ John Locke

Virtue is harder to be got than knowledge of the world; and, if lost in a young man, is seldom recovered.

~ John Locke