To learn to think is to learn to question. Those who don't question never truly think for themselves. These are simple rules that have governed the advancement of science and human thought since the beginning of time. Advancements are made when thinkers question theories(理论) and introduce new ones. Unfortunately, it is often the great and respected thinkers who end up slowing the progress of human thought. Aristotle was a brilliant philosopher whose theories explained much of the natural world, often incorrectly. He was so respected by the scientific community that even 1,200 years after his death, scientists were still trying to build upon his mistakes rather than correct them!

Brilliant minds can intimidate up­and­coming thinkers who are not confident of their abilities. They often believe they are not as good as the minds of giants such as Aristotle, leading many to accept current ideas instead of questioning them.

I, like many thinkers of the past, once believed in my mental weakness. I was certain that my parents, my teachers—adults in general—were always right. They were like a textbook to me; I didn't question what was written on those pages. I respected them, and accepted whatever they told me. But that attitude soon changed. My mind's independence was first developed in the classroom.

A stern, 65­year­old elementary­school science teacher once told me that light is a type of wave. I confidently went through years of school believing that light is a wave. One day，however, I heard the German exchange student mention that light could be made up of particles(粒子). As the others laughed at his statement, I started to question my beliefs.

Maybe the teachers and textbooks hadn't given me the whole story. I went to the library, did some research and learned of the light­as­a­wave versus light­as­a­particle debate. I read about Einstein's discovery of the dual nature of light and learned the facts of a paradox(悖论) that puzzles the world's greatest thinkers to this day. Light behaves as both a particle and a wave, it is both at once. I realized I had gone through life accepting only half of the story as the whole truth.

Each new year brought more new facts, and I formulated even more questions. I found myself in the library after school, trying to find my own answers to gain a more complete understanding of what I thought I already knew. I discovered that my parents and teachers are good tools in my quest for knowledge, but they are never the final word. Even textbooks can be challenged. I learned to question my sources, I learned to be a thinker. I once believed that everything I learned at home and at school was certain, but I have now discovered to re­examine when necessary.

Questions are said to be the path to knowledge and truth, and I plan to continue questioning. How many things do we know for sure today that we will question in the future? At this moment, I know that our sun will burn for another five billion years, and I know nothing can escape the gravity of a black hole. This knowledge, however, may change in the next 20 years—maybe even in the next two. The one thing we can control now is our openness to discovery. Questions are the tools of open minds, and open minds are the key to intellectual advancement.