The key word was "only". Of course you need to turn to your heart. There's no better judge. But it doesn't hurt to know how the mind is "helping" the heart out.
There's a tonne of theories behind that one. I recommend reading Consciousness: A Very Short Introduction by Susan Blackmore.
http://www.amazon.co.uk/Consciousnes...2477957&sr=8-3
It's a very easy read and is fun. It runs through all modern theories of perception.
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You have to.
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Ok, I'll be overly clear.
Let's take the solipsistic ride. Let's say the whole world changes compared to what you have faith in, even for other people. Let's say you're a Buddhist and you have a Christian friend. What happens when your friend dies? Remove solipsism and you have the same situation of just one truth being true.
Here's another one back to our world. Let's do the two doors example. You, (still a Buddhist) is standing next to the same Christian. Behind one of the doors is a leprechaun that gives everybody who passes through a big bag of gold. The other one just smells unpleasant and no gold. The Christian takes the door he has faith is the right one. He gets the leprechaun and the gold. When its your turn to pick, do you do the random choice, or do you go with the same door?
My point with the two examples is that when you assert that you know something, you also assert that everybody else that has a contrary view is wrong. If you claim that they can also be right "in their way", all you've done is asserted that you in fact don't know. You just think it is likely. It's totally fair to say, "this is what I think/hope is right, but I may be wrong". But this isn't "knowing what is true" aka faith. It's simply narrowing down the alternatives.
There's an extremely fun quote from an early female logician who's name escapes me. She said in a letter to Bertrand Russel, "I've recently taken up solipsism. I don't understand why more doesn't do it". The point being that, if you're a solipsist, everybody else that doesn't agree with you, you know are always wrong, so it doesn't really matter if they're solipsist too. I don't think she was really a solipsist.