The Arabic word "Islam" means capitulation, deliverance or submission. We will restrict our attention to the meaning "submission". To answer the question as to what Islam is, we have to answer the question as to what or to whom you have to submit as a Muslim. The adherents of Islam today would normally answer this question by saying, "To be a Muslim you have to submit to Allah, to the Koran and to Muhammad." According to this definition Abraham was no full Muslim, because the Koran and Muhammad came after Abraham and you need the Koran and Muhammad to be a real Muslim in the present meaning of Islam.