I would like to explore certain kinds of experiential knowledge that appear to me to be difficult to investigate rationally as the rational attitude itself might be the cause of a reluctance to explore. If this is already covered in one of the articles on the site please refer me to it.
In this thought experiment we will use the example of lucid dreaming. Lucid dreaming is a state in which a person realises they are dreaming while they are dreaming. The subtleties of the state are not relevant to this discussion.
 We will assume the experiment takes place at a time where the existence of the experience of lucid dreaming hasn't been scientifically proven yet. We will also assume that a proof is not possible in the current state of technological or methodological development.
 Person A has a (true) belief on the existence of lucid dreaming that is based on his personal experience of the state.
 He is trying to communicate the existence of lucid dreaming to someone else. Let us call him person B.
 Actually becoming lucid in a dream is quite a complex process that requires among other things1:
[4.1] Expending large amounts of effort.
[4.2] Following guidelines and exercises that appear strange.
[4.3] A time investment of significant length.
In the described circumstances we have an internal experience that has not be scientifically proven but is nevertheless true. We know this in our time through scientific studies but B does not know it in his world. Person B would have to actually believe in the existence of lucid dreaming and trust A to guide him through the process. But since there is no sufficient evidence to support the claim of A, the required effort is significantly large and the methods appear strange to those not understanding the state how can B rationally decide to expend the effort?
 People focusing on rational assessment can be mislead when dealing with experiential knowledge that is not yet scientifically proven, is not easily testable and has no obvious external function but is, nevertheless, experientially accessible.
1 Even if you disagree with the level of difficulty or the steps required please accept  and its sub-headings as being accurate for the duration of the argument.