Each undervalues that part of the materials of thought with which he is not familiar.
Interpretation
People tend to underestimate ideas and concepts they are not familiar with.
John Stuart Mill's quote highlights a common psychological bias where individuals dismiss or undervalue those aspects of knowledge or thought that are outside their own experience or familiarity. This reflection on human perception emphasizes the importance of being open-minded and recognizing the value in diverse ideas, as our understanding of the world is often limited by our own experiences and knowledge base.
In practice
In a discussion about innovative solutions, one might quote Mill to encourage others to consider unfamiliar ideas.
The peculiar evil of silencing the expression of an opinion is, that it is robbing the human race; posterity as well as the existing generation; those who dissent from the opinion, still more than those who hold it. If the opinion is right, they are deprived of the opportunity of exchanging error for truth: if wrong, they lose, what is almost as great a benefit, the clearer perception and livelier impression of truth, produced by its collision with error.
As for charity, it is a matter in which the immediate effect on the persons directly concerned, and the ultimate consequence to the general good, are apt to be at complete war with one another.
To think that because those who wield power in society wield in the end that of government, therefore it is of no use to attempt to influence the constitution of the government by acting on opinion, is to forget that opinion is itself one of the greatest active social forces. One person with a belief is a social power equal to ninety-nine who have only interests.
There should be perfect freedom, legal and social, to do the action and stand the consequences. It would be a great misunderstanding of this doctrine to suppose that it is one of selfish indifference, which pretends that human beings have no business with each other's conduct in life, and that they should not concern themselves about the well-doing or well-being of one another, unless their own interest is involved.
Political Economy, in truth, has never pretended to give advice to mankind with no lights but its own; though people who knew nothing but political economy (and therefore knew it ill) have taken upon themselves to advise, and could only do so by such lights as they had.
Marriage is the only actual bondage known to our law. There remain no legal slaves, except the mistress of every house.
I have not seen a person who loved virtue, or one who hated what was not virtuous. He who loved virtue would esteem nothing above it.
When the eye is unobstructed, the result is sight. When the ear is unobstructed, the result is hearing. When the mind is unobstructed the result is truth. When the heart is unobstructed, the result is joy and love.
Men get opinions as boys learn to spell by reiteration chiefly.
I learned the most important lesson of my life: that the extraordinary is not the birthright of a chosen and privileged few, but of all people, even the humblest. That is my one certainty: we are all the manifestation of the divinity of God.
Until the juice ferments a while in the cask, it isn't wine. If you wish your heart to be bright, you must do a little work.
When we forgive evil we do not excuse it, we do not tolerate it, we do not smother it. We look the evil full in the face, call it what it is, let its horror shock and stun and enrage us, and only then do we forgive it.
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