If no force acts upon an object at rest, it will remain at rest. This is a fundamental principle of physics known as Newton's First Law of Motion, also known as the Law of Inertia.

Here's why:

* Inertia: Inertia is the tendency of an object to resist changes in its motion. Objects at rest want to stay at rest, and objects in motion want to stay in motion at a constant speed and direction.

* Force: A force is a push or pull that can change an object's motion.

* No Force, No Change: If there's no force acting on the object, there's nothing to overcome its inertia. So, the object will remain at rest.

Example: Imagine a book sitting on a table. If you don't push or pull it, it will stay right where it is. It's not moving because there's no force acting upon it to make it move.