Imagination

One of the most important mental tools that humans have might be our abilities to imagine. I think it's what separates us from other animals who are only capable of thinking of very basic instincts. If they are hungry, then they must find food to eat. If they are thirsty, they need to find water to drink. If they are tired, then they must sleep. But most humans don't function so simply.

These things are just survival instincts, but imagination allows us to have more complex psychological thought processes. Without doing anything but closing my eyes and focusing, I can imagine that I am the king of the world with a castle full of servants. I can also pretend I am a beggar on the streets in the same way. This power that we have as humans is what allowed us to advance past other animals. They are only interested in their own survival, but the imagination inside of us may be what caused curiosity.

How many bricks can I stack on top of each other to create more floors in this building? What happens if I combine two sticks to make a compass? Is it possible to divide this number rather than simply subtracting from it to make it smaller? All of these questions and countless more made us go one step further at a time to amount to the civilisation that we are today.