Probably the greatest difference among men is this difference in habits of thought. There are some minds which behave merely like the mechanic who having learned his trade in a certain way never can function in any other.

I Have often thought if the minds of men were laid open, we should see but little difference between that of the wise man and that of the fool. There are infinite reveries, numberless extravagances, and a perpetual train of vanities which pass through both. The great difference is, that the first knows how to pick and cull his thoughts for conversation, by suppressing some, and communicating others; whereas the other lets them all indifferently fly out in words.

The difference between men is in their principle of association. Some men classify objects by color and size and other accidents of appearance; others by intrinsic likeness, or by the relation of cause and effect. The progress of the intellect is to the clearer vision of causes, which neglects surface differences. To the poet, to the philosopher, to the saint, all things are friendly and sacred, all events profitable, all days holy, all men divine. For the eye is fastened on the life, and slights the circumstance. Every chemical substance, every plant, every animal in its growth, teaches the unity of cause, the variety of appearance.

Truth that has been merely learned is like an artificial limb, a false tooth, a waxen nose; at best, like a nose made out of another's flesh; it adheres to us only because it is put on. But truth acquired by thinking of our own is like a natural limb; it alone really belongs to us. This is the fundamental difference between the thinker and the mere man of learning. The intellectual attainments of a man who thinks for himself resemble a fine painting, where the light and shade are correct, the tone sustained, the colour perfectly harmonised; it is true to life. On the other hand, the intellectual attainments of the mere man of learning are like a large palette, full of all sorts of colours, which at most are systematically arranged, but devoid of harmony, connection and meaning.

The faculty by which man is differentiated from the lower animals is his reasoning power. But the devout believer renounces reason, refuses to explain the things which surround him, the innumerable natural phenomena, because his religious faith is enough for him. The brain loses the habit of thinking; and this religious sottishness hurls mankind back into animalism.

Man bears in his bodily structure clear traces of his descent from some lower form; but it may be urged that, as man differs so greatly in his mental power from all other animals, there must be some error in this conclusion. No doubt the difference in this respect is enormous, even if we compare the mind of one of the lowest savages, who has no words to express any number higher than four, and who uses no abstract terms for the commonest objects or affections, with that of the most highly organised ape.

Man only is endowed with wisdom so as to understand religion, and this is the principal if not the only difference betwixt him and dumb animals; for other things that seem peculiar to him, though they are not the same in them, yet they appear to be alike … What is there more peculiar to man than reason, and foresight? Yet there are animals which make several different ways of retiring from their dens; that when in danger they may escape; which without understanding and forethought they could not do. Others make provision for the future.

You will see...many very important differences between our methods of education and yours, but the main difference is that nowadays all persons equally have those opportunities of higher education which in your day only an infinitesimal portion of the population enjoyed. We should think we had gained nothing worth speaking of, in equalizing the physical comfort of men, without this educational equality....

My object in this chapter is solely to shew that there is no fundamental difference between man and the higher mammals in their mental faculties.

Progress in every country depends mainly on the education of its people. Without education, we are a nation of children. The difference between one man and another, apart from birth and social position, consists in the extent of knowledge, general and practical, acquired by him. We may safely assume that man in all countries within certain limits start with the same degree of intelligence. A civilised nation is distinguished from an uncivilised one by the extent of its acquired intelligence and skill.

The difference between the most dissimilar characters, between a philosopher and a common street porter, for example, seems to arise not so much from nature, as from habit, custom, and education.

One always feels that a merely educated man holds his philosophical views as if they were so many pennies in his pocket. They are separate from his life. Whereas with a cultured man there is no gap or lacuna between his opinions and his life. Both are dominated by the same organic, inevitable fatality. They are what he is.

There is no doubt that the contrast is patent between what we call, with too gross a classification, the developed and the undeveloped countries... Why is there this difference, this divergence, this bifurcation? ... [I]t is not due to any difference in intellectual capacity, human ability or insight. It is an absurd notion that the European is intellectually superior to vast millions of the human race in Asia and elsewhere. The subtlety, the insight, the power of reflection and of argument to be found in India and elsewhere are equal to anything which is within our conception or grasp. As for character and human ability, it would be ludicrous, and a confession of total and boorish ignorance, to say that it is difference in those respects which accounts for these differences of experience. In case I be misunderstood, may I say at once that I do not believe that the IQ method of analysing the human race produces useful results for this purpose. I doubt whether many of the characteristics which we regard as typically and transcendentally European are purely intellectual. I think they have in them very much of the moral and very much of the social.

Mother, recently I have discovered the one way in which human beings differ completely from other animals. Man has, I know, language, knowledge, principles, and social order, but don't all the other animals have them too, granted the difference of degree? Perhaps the animals even have religions. Man boasts of being the lord of all creation, but it would seem as if essentially he does not differ in the least from other animals. But, Mother, there was one way I thought of. Perhaps you won't understand. It's a faculty absolutely unique to man - having secrets. Can you see what I mean?