Since Islam originated from monotheism...

Since Islam originated from monotheism, it conceived idolatry as its real enemy and acted with the purpose of subduing it first in the Arab lands and then throughout the world. The Qur'an accepts Christianity and the Jewish religion as divine religions; therefore, it did not instigate any struggle against them. However, Christianity first conceived of Islam as a competitor and, therefore, attacked it directly.

The Arian and Nestorian sects of Christianity had a positive outlook on Islam since they were monotheistic in outlook. As compared to Islam the doctrine of the Trinity and the Monophysite mode of thinking retained the residues of idolatry. The places of ancient Jupiter, Apollo, Venus were given to God, Jesus, and Mary. Since iconoclasticism of Islam was against their frame of mind, the Christians started a religious struggle against Islam.

The following verses from the Qur'an indicate that in Islam there is no obligatory doctrination but religious tolerance: Lakum din-u-kum wa li-ya din (you have your religion and I have mine); la ikra'ha fi al-din (religion is not to be forced on anyone). On the other hand, the idea of proselytism is dominant in Christianity. Christianity indoctrinates that it is the only way to spread and spreading is its main duty.

In spite of this principle in Christianity, the spread of Islam in all domains from the first Hijrah on not by wars but sporadically was much more rapid.

Barthold sees the reason for this in the capacity of the Arabic language and in the Islamic custom of not collecting taxes and duties from defeated nations if they accepted Islam.[^4] Although these sociological factors play a significant role, the ease in accepting a natural and rational religion and its consistency with human idealism are additional reasons for the spread of Islam. The Christian reaction to Islam in the East and West took different forms.

Those who criticized the new religion vehemently and did not wish to accept it as a religion at all come first. John of Damascus in his book De Haeresibus, considered Islam to be heresy. The first Byzantine writer who referred to the Prophet was Theophanes the Confessor (202/817). He also attacked Islam as severely as John. Guilbert de Nogent's (518/1124) criticism was based on the fact that wine and pork were tabooed in Islam.

As an exception, Hilderbert de Lemans for the first time, in the Middle Ages in the West, stated that Muhammad was a real Prophet and he did produce miracles.