It is a dangerous error to confound truth with matter-of-fact. Our life is governed not only by facts, but by hopes; the kind of truthfulness which sees nothing but facts is a prison for the human spirit. Dreams are only to be condemned when they are a lazy substitute for an effort to change reality; when they are an incentive, they are fulfilling a vital purpose in the incarnation of human ideals. To kill fancy in childhood is to make a slave to what exists, a creature tethered to earth and therefore unable to create heaven.

Bertrand Russell (1872-1970) English mathematician and philosopher

Education and the Good Life, Part 2, ch. 5 “Play and Fancy” (1926)
    (Source)

On children's literature.