The incestuous relationship of the Ego, attached to the Body, gives birth to a daughter called Desire. When she is grown up and attains to puberty, she is mated to Hatred. The child of this marriage, nursed by its grand parent, Pride, the father of Ego, is the reaction to pleasure and pain (the duality of good and bad). This monster, fed on Hope, gets fattened and is violently opposed to Courage and Self-control - and being always drunk in Discontent, seeks delight in the chamber of Sensuality. Its (Duality's) sole work is to spread the disease of Doubt, without which it cannot exist, and in the process cuts out many a by-path of evil deeds. Thus it is that a person, being misguided, moves in the jungle of worldly life and bears through it heavy blows of misery.
This diseased family is known to exist and prosper through eternity. Like infection, it survives by afflicting the human mind, and spreads its tentacles without our knowledge. You must have observed in practical life that the doubting Thomas is always a man with a strong ego. Have you ever seen a fool or an idiot who is humble? See the happy countenance of contentment that sits ever so lightly on the face of a man of humility.