Humans are quite proud of their intelligence. Being smart is a measure of people, just like being strong or healthy. It can increase not only the likelihood of survival but of breeding as well. Unfortunately, it is not easily defined.
We have all met people who were labeled smart but were also total morons. The stereotype is the super science geek who can rattle on about physics but can barely tie his own shoes. Obviously, intelligence is not measured in one fashion.
Many animals are considered intelligent in their own way. Cuttlefish and octopuses exhibit extraordinary control of their bodies in reaction to detailed awareness of their surroundings. They have also exhibited curiosity and the ability to learn quickly. They do all of this without the centralized brains that humans have. Of course, I haven't heard of them reading LibertyBob.com, so they can't be too bright.
Intelligence is also separate from education. Despite our delusions to the contrary, being educated only guarantees a certain level of intelligence. I have met many educated people who could not think their way through an open door. On the other hand, I have known a great number of intelligent people who lacked education who could not only go through open doors but were capable far greater things. Formal education is like an infectious disease; you can expose everybody to knowledge but not everyone will catch it.
So, where does that leave us?
In times past, when less thought was given to not offending everyone, persons who had an obvious lack of intellect were referred to as being simple. In this arcane description, we may find a kernel of possibility.
Though computers are not actually intelligent and cannot think in any capacity, they will serve for the purpose of illustration. Imagine two chess-playing computers. One is a little, hand-held device that runs a simple program. The other computer is a huge super-computer designed to play chess competitively on the world stage. The first is obviously a simpler computer and though it can play chess it has much less capacity to win. The super-computer is a far more complex machine, and is far more likely to win.
You can see this in humans. The developmentally disabled can only understand simple concepts and instructions. They can still perform tasks, but if the task becomes too complex the person cannot continue effectively. A person like Leonardo di Vinci, who can sculpt, paint, write, engineer, and more, is obviously capable of greater complexity. These two extremes are easy to see.
Where does that leave everyone else? Not everyone is extremely simple, and the world has few Leonardo di Vincis. Where is this middle ground? Well, I have bad news for you. It is distributed between the two extremes.
That's right, everyone you know who is not in one of the extremes is somewhere in between. You will have to figure out where. Most everyone will be near the middle; this is just the way people average out. Are you near the middle on the above average side or on the other side? That's a good question.
You probably know a few people who are between the middle and one of the extremes. There was that kid in school who got all As but wasn't the total geek. You may know a political ranter who can argue two contradictory philosophies as long as he is arguing them on separate occasions. The important thing to remember is that half the people are of below-average intellect.
If you are concerned about your position on the spectrum, there are a couple of things you can do. First, exercise your brain. Take classes or read a wide variety of books. Don't rely entirely on conversation because you may be one of those morons who will only waste the other person's time.
Secondly, you can try to learn where you really fall on the scale. Don't rely on IQ tests; those are notoriously flawed and unreliable. Instead, see how people respond to your accomplishments. If your college degree says Summa Cum Laude, there is a good chance that you are in the upper half. If the others just smile at you and tell you that you are special, maybe you fall in the lower half.
Try not to get too hung up on intellectual capacity. The success and correctness of a human being does not necessarily rely on brains. We are animals on the path of birth, breeding, and death. I can guarantee you that right now I am capable of far greater thoughts than Leonardo di Vinci. That's because he is long dead. Someday, you will be too.