A more thorough explanation:

The predictive theory of law is the idea that the law is simply a set of predictions about what the courts will decide in certain situations. This theory was famously expressed by Oliver Wendell Holmes in his article "The Path of the Law."

For example, if someone is accused of stealing, the law predicts that the court will decide whether or not the person is guilty based on the evidence presented. The law does not dictate the outcome, but rather predicts what the court will decide.

This theory is also known as the prediction theory and is often contrasted with the bad-man theory, which suggests that the law is a set of rules that people follow to avoid punishment.