A radar does not detect itself. It is not sensitive to its user, its own wave guides, or the machinery which translates its responses into a reality -- the machinery of tube, screen, interpretative opinion of the user, etc.
Beliefs, likewise, constitute a "machinery of perception" which can be invisible to itself. But the owner needs to know they are there. He might otherwise be mystified by the fact that every time he walks onto the bridge, that funny TV image is there on the screen, coming from god only knows where!
A large part of the difficulty of becoming more 'enlightened' than one is lies in discovering those structures of belief which are so close to one's 'self' as to be transparent. When they are discovered, through meditation, therapy, or other applications of awareness, they dissolve in gales of laughter at the difficulties they caused. Finding them, especially unaided, is the hard part.
Therapy is often reversed in its results because the practitioner requires the acceptance of beliefs and labels (which in turn carry beliefs with them) by the recipient. This not only adds other-determined information to the recipient's universe, which is against his best interests, but makes it more difficult than ever for him or her to discover the invisible belief structures which are flooding him with the unwanted experiences of introversion, dissonance, depression, or neurosis.
To find invisible beliefs one must be willing to elevate his feeling ability to be able to experience them, without judgment. When judgment is suspended, the facts of belief become evident. This can be prompted by noticing what one is experiencing and focusing on the question of what beliefs would prompt such an experience.