A mystical experience is one which we experience...but not directly through sensory means.
Rational thinking requires sensory inputs. Mystical experiences are not amenable to that. Therefore they can only be speculated on...through philosophical concepts. PLease see my thread on Faith.
Why would thinking require specific sensory input? If speculation is not rational, it is incoherent.
There's also an element of poisoning, or rather in this caee sweetening the well by using the term 'mystical'. You seem to be referring to a split between external experiences and internal ones. Attaching the title 'mystical' is just indulging in a preconceived idea.