First of all;
Do not despair of God's Mercy. [Qur'an 39:53]
Secondly, you should know that we Muslims, who are students of the Qur'an, follow proof; we approach the truths of belief through reason, thought, and our hearts. We do not abandon proof in favour of blind obedience and imitation of the clergy like some adherents of other religions. Therefore, in the future, when the intellect, science and technology prevail, of a certainty, that will be the time the Qur'an will gain ascendancy, which relies on rational proofs and invites the intellect to confirm its pronounce
Thirdly, know that history, which records actual events, is the most faithful witness to the truth.
History shows that the Muslims increased in civilization and progressed in relation to the power of the truths of Islam; that is, to the degree that they acted in accordance with that power. And history also shows that they fell into savagery and decline, and disaster and defeat amidst utter confusion to the degree of their weakness in adhering to the truths of Islam. As for other religions, it is quite to the contrary. That is to say, history shows that just as they increased in civilization and progressed in relation to their weakness in adhering to their religions and bigotry, so were they also subject to decline and revolution to the degree of their strength in adhering to them. Up to the present, time has passed thus.
Furthermore, from the blessed time of the Prophet (PBUH) up to the present, not a single event in history has shown us a Muslim who has embraced another religion, whether old or new, in preference to Islam, as a result of reasoned argument and conclusive evidence. If the uneducated embrace another religion without evidence in blind imitation, it has no bearing on this matter. And to be without religion is yet another question. However, history shows us that followers of other religions, and even the English and pre-Revolution Russians, who displayed the greatest bigotry in religion, are gradually approaching and entering Islam on the strength of reasoned argument and cogent proofs, sometimes in groups.
Since Islam relies on reason and reasoned proof, it is the religion of the present and the future, for this is the age of science, technology and reason. This fact is being understood now by many who realize that they cannot live without a true and complete religion. The causes for the decline of the Islamic world and its material backwardness in comparison to the West should be sought in the failure of Muslims to adhere to the teachings and truths of the Holy Qur'an and Islam. Just as Islam provides for the material progress of man, and indeed urges him towards it, so too does it provide for man true progress and development in moral and spiritual matters. This combination forms the basis of true civilization.
"If we were to display through our actions the perfections of the moral qualities of Islam and the truths of belief, without doubt, the followers of other religions would enter Islam in whole communities; rather, some entire regions and states, even, on the globe of the earth would take refuge in Islam."