Perhaps then we shall stop pretending that we know everything, and shall be less bold in raising questions and getting
into confusing disputes with others about things to which
our understandings are not suited — things of which we can’t
form any clear or distinct perceptions in our minds, or, as
happens all too often, things of which we have no notions at
all. If we can find out what the scope of the understanding
is, how far it is able to achieve certainty, and in what cases
it can only judge and guess, that may teach us to accept our
limitations and to rest content with knowing only what our
human condition enables us to know.

Opinion is the medium between knowledge and ignorance

I remember it was with extreme difficulty that I could bring my master to understand the meaning of the word opinion, or how a point could be disputable; because reason taught us to affirm or deny only where we are certain; and beyond our knowledge we cannot do either.

...[S]ome of the opinions which people entertain should be respected, and others should not.

It does take great maturity to understand that the opinion we are arguing for is merely the hypothesis we favor, necessarily imperfect, probably transitory, which only very limited minds can declare to be a certainty or a truth.

I think we ought always to entertain our opinions with some measure of doubt. I shouldn't wish people dogmatically to believe any philosophy, not even mine.

There are in fact two things, science and opinion; the former begets knowledge, the latter ignorance.

The respect for authority, the presumption in favor of those who have won intellectual reputation, is within reasonable limits, both prudent and becoming. But it should not be carried too far, and there are some things especially as to which it behooves us all to use our own judgment and to maintain free minds. For not only does the history of the world show that undue deference to authority has been the potent agency through which errors have been enthroned and superstitions perpetuated, but there are regions of thought in which the largest powers and the greatest acquirements cannot guard against aberrations or assure deeper insight. One may stand on a box and look over the heads of his fellows, but he no better sees the stars. The telescope and the microscope reveal depths which to the unassisted vision are closed. Yet not merely do they bring us no nearer to the cause of suns and animal-cula, but in looking through them the observer must shut his eyes to what lies about him. That intension is at the expense of extension is seen in the mental as in the physical sphere. A man of special learning may be a fool as to common relations. And that he who passes for an intellectual prince may be a moral pauper there are examples enough to show.

The duty and the right to express one's opinion freely may be meaningless—and on occasion even injurious to the best interests of the society—if those opinions are not based on sound thought, which, in its turn, presupposes the possession of sound knowledge.

if any opinion is compelled to silence, that opinion may, for aught we can certainly know, be true. To deny this is to assume our own infallibility.

It is rare that the public sentiment decides immorally or unwisely, and the individual who differs from it ought to distrust and examine well his own opinion.

Seek out the smartest people who disagreed with me so I could try to understand their reasoning. 2. Know when not to have an opinion. 3. Develop, test, and systemize timeless and universal principles. 4. Balance risks in ways that keep the big upside while reducing the downside.

What we should do, I suggest, is to give up the idea of ultimate sources of knowledge, and admit that all knowledge is human; that it is mixed with our errors, our prejudices, our dreams, and our hopes; that all we can do is to grope for truth even though it be beyond our reach. We may admit that our groping is often inspired, but we must be on our guard against the belief, however deeply felt, that our inspiration carries any authority, divine or otherwise. If we thus admit that there is no authority beyond the reach of criticism to be found within the whole province of our knowledge, however far it may have penetrated into the unknown, then we can retain, without danger, the idea that truth is beyond human authority. And we must retain it. For without this idea there can be no objective standards of inquiry; no criticism of our conjectures; no groping for the unknown; no quest for knowledge.

Timidity betrays want of powers, and audacity a want of skill. There are, indeed, two things, knowledge and opinion, of which the one makes its possessor really to know, the other to be ignorant.