Mental development must be ...

Mental development must be connected with movement and be dependent on it. It is vital that educational theory and practice should be informed by that idea.
Mental development must be connected with movement and be dependent on it. It is vital that educational theory and practice should be informed by that idea.

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If one does not know to which port one is sailing, no wind is favorable.
What a distressing contrast there is between the radiant intelligence of the child and the feeble mentality of the average adult.
We are masters of the unsaid words, but slaves of those we let slip out.
I have always found that mercy bears richer fruits than strict justice.
A lie gets halfway around the world before the truth has a chance to get its pants on.

Quotes from the same author

Everyone in the world ought to do the things for which he is specially adapted. It is the part of wisdom to recognize what each one of us is best fitted for, and it is the part of education to perfect and utilize such predispositions. Because education can direct and aid nature but can never transform her.
At birth, the child leaves a person - his mother's womb - and this makes him independent of her bodily functions. The baby is next endowed with an urge, or need, to face the out world and to absorb it. We might say that he is born with 'the psychology of world conquest.' By absorbing what he finds about him, he forms his own personality.
This is education, understood as a help to life; an education from birth, which feeds a peaceful revolution and unites all in a common aim, attracting them as to a single centre. Mothers, fathers, politicians: all must combine in their respect and help for this delicate work of formation, which the little child carries on in the depth of a profound psychological mystery, under the tutelage of an inner guide. This is the bright new hope for mankind.
To give a child liberty is not to abandon him to himself.
A humankind abandoned in its earlier formative stage becomes its own greatest threat to survival.