It is notorious that facts are compatible with opposite emotional comments, since the same fact will inspire entirely different feelings in different persons, and at different times in the same person; and there is no rationally deducible connection between any outer fact and the sentiments it may happen to rpovoke. These have their source in another sphere of experience altogether, in the animal and spiritual region of the subject's being. Conceive yourself, if possible, suddenly stripped of all the emotion with which your world now inspires you, of all the emotion with which your world now inspires you, and try to imagine it as it exists, purely by itself, without your favorable or unfavorable, hopeful or apprehensive comment. It willb e almost impossible for you to realize such a condition of negativity and deadness. N o one portion of the universe would hten have importance beyond another; and the whole colection of its things and series of its events would be without significance, character, expression, or perspective. Whatever of value, interest, or meaning our respective worlds may appear endued with are thus pure gifts of the spectator's mind. The passion of love is the most familiar and extreme example of this fact. If it comes, it comes; if it does not come, no process of reasoning can force it. Yet it transforms the value of the creature loved as utterly as the sunrise transforms Mont Blanc from a corpse-like gray to a rosy enchantment; and it sets the whole world to a new tune for the lvoer and gives a new issue to his life. So with fear, with indignation, jealousy, ambition, worship. If they are there, life changes. And whether they shall be there or not depends almost always upon non-logical, often on organic conditions. And as the excited interest which these passions put into the world is our gift to the world, just so are the passions themselves gifts,--gifts to us, from sources sometimes low and sometimes high; but almost always non-logical and beyond our control.
William James, The Varieties of Religious Experience, Lectures VI and VII: "The Sick Soul." James goes on to note that the withdrawal or degeneration of our own contribution to the interaction of the world introduces a pathological condition just as surely as the withdrawal or degeneration of the world's contribution.
James's book is, of course, the most famous and best-selling Gifford Lectures ever published (and still is an easy candidate for the top ten Gifford Lectures of all time).