Most readers will recognise this to be true of poets, but will doubt its application to philosophers, because imperfect psychology and unscientific criticism have disguised the identity of intellectual processes until it has become a paradox to say that imagination is not less indispensable to the philosopher than to the poet.  The paradox falls directly we restate the proposition thus:  both poet and philosopher draw their power from the energy of their mental vision—­an energy which disengages the mind from the somnolence of habit and from the pressure of obtrusive sensations.  In general men are passive under Sense and the routine of habitual inferences.  They are unable to free themselves from the importunities of the apparent facts and apparent relations which solicit their attention; and when they make room for unapparent facts it is only for those which are familiar to their minds.  Hence they can see little more than what they have been taught to see; they can only think what they have been taught to think.  For independent vision, and original conception, we must go to children and men of genius.  The spontaneity of the one is the power of the other.  Ordinary men live among marvels and feel no wonder, grow familiar with objects and learn nothing new about them.  Then comes an independent mind which sees; and it surprises us to find how servile we have been to habit and opinion, how blind to what we also might have seen, had we used our eyes.  The link, so long hidden, has now been made visible to us.  We hasten to make it visible to others.  But the flash of light which revealed that obscured object does not help us to discover others.  Darkness still conceals much that we do not even suspect.  We continue our routine.  We always think our views correct and complete; if we thought otherwise they would cease to be our views; and when the man of keener insight discloses our error, and reveals relations hitherto unsuspected, we learn to see with his eyes and exclaim:  “Now surely we have got the truth.”

III.

A child is playing with a piece of paper and brings it near the flame of a candle; another child looks on.  Both are completely absorbed by the objects, both are ignorant or oblivious of the relation between the combustible object and the flame:  a relation which becomes apparent only when the paper is alight.  What is called the thoughtlessness of childhood prevents their seeing this unapparent fact; it is a fact which has not been sufficiently impressed upon their experience so as to form an indissoluble element in their conception of the two in juxtaposition.  Whereas in the mind of the nurse this relation is so vividly impressed that no sooner does the paper approach the flame than the unapparent fact becomes almost as visible as the objects, and a warning is given.  She sees what the children do not, or cannot see.  It has become part of her organised experience.