Hippocrates is often called the father of medicine. Why is that so? What were his contributions?

Hippocrates was a Greek doctor who lived during the Age of Pericles in Classical Greece. Hippocrates is considered the "Father of Medicine" both for his medical philosophies and clinical methods. However, it can be argued that his philosophy of medicine was more important because it set the foundation into establishing the medical profession.
He is also the founder of the Hippocratic School of Medicine. The Hippocratic Oath is named after him, which is a still-used universal medical oath that new physicians swear by upon entering the profession.
While the true extent of Hippocrates' contribution to the medical practice is still being debated by historians and other scholars, it is mostly agreed upon that he set the foundation for the proliferation of medial knowledge. The Hippocratic Corpus is a body of work, written in Ionic Greek, that compiles medical knowledge during his time, which was built upon the clinical theories and methodologies from ages prior. It can be argued that medical schools today wouldn't exist, or would look very different, if it weren't for Hippocrates' idea to collect and expand upon prior medical knowledge.
Although the medical field has progressed exponentially throughout the centuries since Hippocrates' time, his ideas on how physicians should conduct themselves professionally are still practiced today. Likewise, his emphasis on continuing to build medical knowledge is the foundation of contemporary medical education.
http://iv.iiarjournals.org/content/23/4/507.full.pdf