Mathematics as a discipline
Mathematics, as a science, is one of the oldest known forms of logical thinking by mankind. Since ancient Mesopotamia and likely before (3,000 BCE), humans have been relying on arithmetic and more challenging forms of math to answer life's biggest questions.
Today, we rely on math for most aspects of our daily life; yes, I know that sounds cliché, but I mean it. Whether you are watering your plants or feeding your dog, your internal mathematical engine is constantly spinning—calculating how much water the plant had per day over the last week and predicting the next time your dog will be hungry given that they eat right now. Whether or not you are consciously using the principles of math, the concepts live deep inside everyone's brains. It's my job as a math teacher to get you to realize it.