As you know doubt or as you no doubt?

if your referring to the band, its no doubt. and if your talking about the expression, it is also no doubt.

Yes actally....very wise.

If you have to ask this question, you probably do. If you knew, you'd have no second thoughts(:

Both are correct, and other possibilities exist. This is because "no doubt" is what we call absolute: it has no grammatical connection to the rest of the sentence. There might be variations in...

You can't. The end. You can believe, or have faith that there is one according to a religious concept of heaven, but there is no concrete way of proving or disproving something like heaven.