Quote from A Course in Miracles Text Chapter 6, Section 5 - The Only Answer.

When God created you He made you part of Him. That is why attack within the Kingdom is impossible. You made the ego without love, and so it does not love you. You could not remain within the Kingdom without love, and since the Kingdom is love, you believe that you are without it. This enables the ego to regard itself as separate and outside its maker, thus speaking for the part of your mind that believes you are separate and outside the Mind of God. The ego, then, raised the first question that was ever asked, but one it can never answer. That question, "What are you? " was the beginning of doubt. The ego has never answered any questions since, although it has raised a great many. The most inventive activities of the ego have never done more than obscure the question, because you have the answer and the ego is afraid of you.

(http://www.schoolforpeace.co.za/)