Alfred Marshall was motivated to understand the underlying principles of economics, believing that poverty was degradating to society. He sought to create an all-encompassing model of economic relationships, combining existing theories and reconciling them. This was a noble project, which for various reasons he could not complete.
Marshall was successful in various areas, though. He had an understanding that economics needs to be based on mathematical principles in order for it to become a respected scientific discipline. Thus, he played an important role in the development of economics as an independent, academic area of study. He was also aware that complex mathematical reasoning was inaccessible to the general public, and was able to craft his ideas in terms that were founded on sophisticated theoretical reasoning yet readily understandable to the reader.
He also tried to reconcile two schools of economic thought, the marginalist and classical. His insight that factors of both supply and demand are important in establishing price was true; however his ability to combine the thought of his British colleagues with the continental Europeans caused his reconciliation to be incomplete. Unification thought explains that the subjective aspect of value to the consumer, well understood by the Austrian school, must always be considered together with the objective "real" value of any item. Thus, Marshall's proposal that time determines whether subjective utility or real cost is the determining factor is not the whole picture.