Why are differential equations used for expressing the laws of physics?

Almost all theories of physics have expressed physical laws by means of differential equations. One can ask: why differential equations? What is special about them? This article addresses these questions and is presented as an inquiry-based lecture, where students and a teacher are engaged in discussion. It has two goals: (1) To help undergraduate students understand the rationale behind the use of differential equations in physics, (2) To show how meaningful and interactive presentation of mathematics can help students take pleasure in learning physics.