The Interface Segregation Principle is about keeping to the contract of interaction presented by your class small. More than small, the contract presented by your class should have a single responsibility.

Sometimes, having a class with a small single responsibility contract is difficult or not desired. In those instances, the class should implement multiple contracts instead of creating a combined contract. We want multiple contracts to reduce the number of far-reaching dependencies.

Every time a base class or interface is modified, the child classes must also be modified. At the very least, the child classes must now be recompiled. By limiting the scope of a contract, we can reduce the impact of changing that contract and improve the overall system architecture.