Wa alaikum assalaam Najimuddin,
(smile) I'm not quite sure what is meant by "belief systems".
But I do know what I believe to be true. And I also know that I may be honestly mistaken. And that I try to live my life walking the best Path that I can. What others believe and try is their own Path.
(smile) I have read that there have been great and knowledgeable scholars who have been reluctant to issue fatawa, for fear of pronouncing wrongly. And that there is a tradition among Islamic scholars to acknowledge that their opponents might be correct, and they themselves incorrect, and that only Allah truly Knows. And this humility (when sincere) has touched me. I admire it.
(smile) I find that it is all too easy to get caught up in one's own truths, and to start feeling the silky tendrils of self-satisfaction. And I believe this to be a very subtle ploy of Shaitan. So I prefer to try to keep an open mind to everyone around me. For while I might have a chunk of Truth, others may have contributions. That I can learn from, though not always directly.
(smile) I read a children's story many years ago, that I have read variations of over the years. Some say it is Sufi in origin, and others claim otherwise. But whatever the reality, it is a powerful story. Here it is:
Once upon a time, there were a group of mice, and they went to discover what an elephant was like. Now this elephant was in a dark room, and the mice could not see it. But they could feel it. One mouse explored the elephant's leg. And another, it's tail. A third explored it's ears, and another, it's trunk. Then the mice left the room and discussed the matter together. The first one said: an elephant is like a tree! But the second said: no, no, it is like a rope! The third one rolled it's eyes in disbelief and squeaked: what are you saying? Of course, it is like a fan! And the last mouse cried: A fan?! No, no, it is like a snake!
All the mice had an element of the whole, but none had more than a part. So who was right?
(smile) I have stated that I do not believe in Infallible Imams. Nor do I believe that God is divisible. (smile) And I have quite a few other core beliefs, that I believe are consonant with core Sunni beliefs. But I also believe that the other person I face has something to teach me. That Allah has not introduced this person into my life for no reason. That through this person, I am being given the opportunity for learning another small part of Truth. (smile) And through me, the other person has an opportunity, too.
(seriously) And it does not matter whether that person is an atheist or a Jew or a Hindu or an animist, or whatever. There is something there, precious, to learn. Allah Created us in our diversity for a reason. And I honour that. I also believe that only God can decide our fate in the Next Life, and only He can Inform us of what is True and Correct.
This thread started as an expression of the OP's personal belief that the Shia (as a whole) are not Muslims, that he put into the mouths of some recognized scholars. It is my personal belief that he is perhaps doing an injustice to people calling themselves Shia, and also to himself. I have also shown that there are recognized scholars who disagree with him.
(smile) But I do acknowledge that I might be wrong. Perhaps Saleem is right. Perhaps all Shia are not Muslims in Allah's eyes. (seriously) But I would caution that this is a serious thing to say, and one that I would not dare to say.
And I would offer that, whatever the Ultimate Truth on this question, if we believe that we are accountable for how we treat others, all others, keeping an open, loving heart for the understandings of others is a good way to help us avoid becoming smug and perhaps treating others wrongly. (sigh) Because it is a human tendency to treat those they consider as outside "their" group, in less-than-good ways. (sad) And even terrible ways.
Considering the amount of strife in the world, including amongst Muslims (or those who believe themselves to be Muslims, though others may not), I feel that throwing out blanket statements, like this one about Shias not being Muslims, does not help. Indeed, I think that it can help fuel conflicts. (mildly) Given that conflicts tend to cause an awful lot of wrongdoing and suffering on all sides... I believe that it is Pleasing to Allah, that we try to avoid conflicts as much as possible.
(smile) I hope this clarifies my position.
May Allah, the Holy, Guide us and have Mercy on us.