The stupidity is in fact a kind of mental laziness. Often caused by a limitation that the person creates around itself.
If you do not know, all people are smart. Everyone is born with almost the same number of neurons, around 100 billion (with a little variation between men and women). If our brains were compared to an external hard drive, its capacity would be approximately 1 Tera. To give you an idea, it would take at least 500 2G flash drives to store everything that we store in our minds.
The brain retains everything around. Nothing escapes its power of absorption. And in fact, what we call "stupidity" is often related to a few factors:
1) Lack of training
2) Personal rhythm (each person has its speed up processing)
3) Method of learning (each person learns in a different way)
4) like the subject
5) Attention deficit
Overall, we are "stupid" to some things and genius to others. This varies from person to person.
Some examples were Einstein and Thomas Edison, both considered "dumb" and expelled from college for being "covered" too. Another was Henry Ford, whose ignorance and lack of education was the article published in the magazine and a laughingstock.
What I mean by all this? I mean, if you want, you can be the smartest person in this world. What you need to know is what you like to learn and how to learn better. Intelligence is also related to the ability to be the best at a specialty: or mathematics, or arts, or or or music, literature, etc.. Henel was considered a "genius" for having composed "The Messiah" in three weeks.
True education is the understanding of oneself and life. Instruction is not education. I know many people instructed but poorly educated. Being educated is to act wisely, seek success is respecting the rights of others, is to demonstrate knowledge without arrogance, is to have humility and be aware of the opportunities to learn something new that life wants to teach.
Because of all this, the real "dumb" may be precisely those who think they know more and are better than other people say.
"The great problem of mankind is that stupid people are full of certainties and the intelligent are full of doubt"
Therefore, no one is stupid, unless you have closed yourself the ability to learn the lessons of life.
"Only 5% of the population think, 15% think they think, and the remaining 80% would rather die than think" (Thomas Edison)
Hugs.