33- General Classification
For clarification, we divide these senses into two categories (these are relative and man-made terms and classifications): the first group contains seven senses called "visible" senses. In contrast, the second group contains 14 senses, called "concealed" senses. "Visible" senses are those whose tools (organs) are apparent and can be seen with eyes, while concealed senses are those that their tools (organs) are hidden and cannot be seen.
Of course, observing the concealed senses' tools (organs) is also possible through surgery, where surgeons can dissect the brain and find their specific locations. Like leaves, flowers, and stems visible in a plant, and when removing the soil, one can see the roots. Therefore, the tools (organs) for both visible and concealed senses can be seen.
By no means, does this classification imply that "visible" senses do not have concealed parts, and concealed senses have no visible parts. As already mentioned, along with visible tools (organs), "visible" senses have places and tools (organs) in the brain and throughout the nervous system that help humans perceive the sense. Conversely, concealed senses have visible parts, and those are the outward actions manifested from those senses.