«قد يكون السبب بمعنى العلة إذا ثبت العلة بالسبب»
Sometimes sabab is used with the function of illah when the latter is established through the former.
The book considers a person driving an animal that tramples property. The animal lacks the kind of independent legal agency possessed by a human; in the relevant case, the driving is used to connect responsibility to the driver.
This is a specific juristic illustration of terminology, not a universal negligence rule for every animal incident.