According to Swami Vivekananda
Each soul is potentially divine.
The goal is to manifest this Divinity within by controlling nature, external and internal.
Do this either by work, or worship, or psychic control, or philosophy — by one, or more, or all of these — and be free.
This is the whole of religion. Doctrines, or dogmas, or rituals, or books, or temples, or forms, are but secondary details.
So He means the core teaching of the religions is true. Secondary details can of course vary. And terroist views are even not parts of the secondary details of any religion as these are framed by the fanatics.
Leaving aside dogmatic study, and taking a common-sense view of the thing, we find at the start that there is a tremendous life-power in all the great religions of the world.
This then is a fact in the present history of the human race, that all these great religions exist and are spreading and multiplying. Now, there is a meaning, certainly, to this; and had it been the will of an All-wise and All-merciful Creator that one of these religions should exist and the rest should die, it would have become a fact long, long ago. If it were a fact that only one of these religions is true and all the rest are false, by this time it would have covered the whole ground. But this is not so;
If the claims of a religion that it has all the truth and God has given it all this truth in a certain book were true, why are there so many sects? Fifty years do not pass before there are twenty sects founded upon the same book. If God has put all the truth in certain books, He does not give us those books in order that we may quarrel over texts.
So with every religion. I am not against any sect. I am glad that sects exist, and I only wish they may go on multiplying more and more. Why? Simply because of this: If you and I and all who are present here were to think exactly the same thoughts, there would be no thoughts for us to think. We know that two or more forces must come into collision in order to produce motion. It is the clash of thought, the differentiation of thought, that awakes thought. Now, if we all thought alike, we would be like Egyptian mummies in a museum looking vacantly at one another's faces — no more than that! Whirls and eddies occur only in a rushing, living stream. There are no whirlpools in stagnant, dead water.
But so long as mankind thinks, there will be sects. Variation is the sign of life, and it must be there. I pray that they may multiply so that at last there will be as many sects as human beings, and each one will have his own method, his individual method of thought in religion.
But this thing exists already. Each one of us is thinking in his own way, but his natural course has been obstructed all the time and is still being obstructed. If the sword is not used directly, other means will be used. Just hear what one of the best preachers in New York says: he preaches that the Filipinos should be conquered because that is the only way to teach Christianity to them! They are already Catholics; but he wants to make them Presbyterians, and for this, he is ready to lay all this terrible sin of bloodshed upon his race. How terrible! And this man is one of the greatest preachers of this country, one of the best informed men. Think of the state of the world when a man like that is not ashamed to stand up and utter such arrant nonsense; and think of the state of the world when an audience cheers him! Is this civilisation?
Then arises the question: How can all these varieties be true? If one thing is true, its negation is false. How can contradictory opinions be true at the same time? This is the question which I intend to answer. But I will first ask you: Are all the religions of the world really contradictory? I do not mean the external forms in which great thoughts are clad. I do not mean the different buildings, languages, rituals, books, etc. employed in various religions, but I mean the internal soul of every religion. Every religion has a soul behind it, and that soul may differ from the soul of another religion; but are they contradictory? Do they contradict or supplement each other? — that is the question. I took up the question when I was quite a boy, and have been studying it all my life. Thinking that my conclusion may be of some help to you, I place it before you. I believe that they are not contradictory; they are supplementary. Each religion, as it were, takes up one part of the great universal truth, and spends its whole force in embodying and typifying that part of the great truth. It is, therefore, addition; not exclusion.
We are viewing truth, getting as much of it as these circumstances will permit, colouring the truth with our own heart, understanding it with our own intellect, and grasping it with our own mind. We can only know as much of truth as is related to us, as much of it as we are able to receive. This makes the difference between man and man, and occasions sometimes even contradictory ideas; yet we all belong to the same great universal truth.
My idea, therefore, is that all these religions are different forces in the economy of God, working for the good of mankind; and that not one can become dead, not one can be killed. Just as you cannot kill any force in nature, so you cannot kill any one of these spiritual forces. You have seen that each religion is living.
His conclusion therefore is:
Sectarianism, bigotry, and its horrible descendant, fanaticism, have long possessed this beautiful earth. They have filled the earth with violence, drenched it often and often with human blood, destroyed civilisation and sent whole nations to despair. Had it not been for these horrible demons, human society would be far more advanced than it is now. But their time is come.
All His followers believe that Swamiji's spirit is working and will work through many Acharyas to eradicate all hatred and all demeaning of other religions and inspire each one to dive deep into his or her own spiritual practices and to realise the Truth instead of branding other's religions as inferior or other's God as demi-god.