systematic theory refers to the study of common model,structure and rules of a system.It researches same features of various systems,quantitatively discribes their functions by mathematical ways and tries to build theories,principles,and mathematical models for them.It is a new thriving science with logic and mathematics charaters.
有个类似的systematic theology指的是一个宗教方面的研究方法,所以考虑就没用这个词.
供参考.