We do know that Islam is the only true religion but that’s exactly what the Christians and the Jews say about their religions. We say Trinity doesn’t make sense, and it conflicts with man’s natural inclination to worship One true God; but how can you answer a non-Muslim who questions how Muslims can say a Trinity is blindly believing the most illogical thing from the Bible when they believe God has a Chair so huge that it consumes up the skies, the earths and everything else? Aren’t we then blindly believing in the illogical? It’s a part of our ‘iman to believe in it (the Qur’an 2:2-3). Therefore when Muslims believe in such a chair, they cannot possibly claim that they do not believe in something illogical, and the Christians only uphold some illogical beliefs as Trinity. Please comment.
I think that one should delve deeper to find out the rationale behind the claims that are made by different religious groups to establish as to which of them is more convincing. Indeed, it is not only the Jews and the Christians who claim that their religious understanding is correct. Even the pagans of Makkah had the same apparent claim. It is, therefore, imperative that the logic behind the claims should be objectively compared.
One problem with the claims of the other religious groups is in establishing the authenticity of the texts their messages are found in. It is difficult to take a text seriously whose originality is in serious doubt. Besides, we have to look for the real arguments behind each one of them. As for the concept of trinity, it is something not even properly established from the Bible. Jesus Christ cannot be claimed to have made this concept as the foundation of his message. Nowhere in the Bible can one find any clear indication that Jesus (sws) had ever preached the concept. It is Saint Paul, who remained an enemy of Jesus throughout his stay in this world, who propagated trinity. Many Christians dispute the concept even today.
When it comes to the concept of the “Chair”, it is only one group of interpreters who believe that the “Chair” has been used in the literal sense. A more acceptable interpretation of the “Chair” is that it refers to the authority of God Almighty. In other words, the expression, “His Chair covers the entire space of the heavens and the earth” means that He has full authority as a sovereign over everything. Thus, the expression “Chair” is symbolic and not literal.
Courtesy: http://www.islamicissues.info/qa_question.php?qid=132