Final answer:
The cornerstone of western legal thought in Europe after the fall of Rome was the development and influence of Roman law.
Step-by-step explanation:
The cornerstone of western legal thought in Europe after the fall of Rome was the development and influence of Roman law. Roman law introduced the concept of using precedent to shape legal decisions, the idea that laws have a spirit that is sometimes more important than a literal interpretation, and the principle of innocent until proven guilty. These ideas formed the basis for most systems of law still in use in Europe today.