The line between lunacy and wisdom (or common sense) CANNOT be mistaken, confused or even compared to anything else. Even a complete idiot should be able to distinguish between the two.
A lunatic may think for instance that if he adds 2 to 2, there is a possibility the outcome might turn NOT 4; he asks other (less) lunatic close to him (acquaintances, co-workers, family members) and everyone suggested the result is 4. Unable to shake off his lunacy, he sets out to prove everybody is wrong; so he adds 2 to 2 and finds that the outcome is 4; he does it again, and again, and again, and again. His hope is that someday, if he continues to add 2 to 2, the outcome would be different. That’s lunacy!
However, an intelligent individual who adds 2 to 2 and comes up with 4, would confer with others; he might even look for references, patterns or whatever else to help prove or reject the outcome. He would put two apples on one side and another two apples on another side and count them one by one until he gets to 4. At that point, the intelligent man would conclude that 2 + 2 are 4. That’s intelligence!