I believe the "deepest possible way" is the closest answer. I believe philosophy deals with the most fundamental issues while sciences deals with the issues that based on the fundamental issues. This means the laws that govern all science issues are based on the fundamental laws that govern the whole universe. The study of philosophy is to look into these fundamental laws.

It can be traced back to the origin. In the ancient Greece, philosophy was defined as "love wisdom" but this term is very ambiguous. Human being uses their wisdom to do all things for example, use wisdom to do cunning things. But this is not philosophy. What the Greeks meant was to perform intellectual activities to search for the answer from environment (external and internal). The whole process of this activity was defined as philosophy, for example, "what compose our world" and methodologies including rhetoric and dialectic. But later, the division of looking into the environment was classified as natural philosophy which now has been changed to the term of science. From the medieval time, Human being's approach to look for answer have developed into the so-called "scientific approach" which is more accurate compared with the ancient time but still falls into the fundamental approach of how to understand the world. When the new approach of looking into the world was formed, many new science developments were achieved. Science as a breakaway division of philosophy left philosophy as a study looking to the most fundamental rules governing our world. That is why philosophy covers much larger system while science only covers their subsystem, a much smaller area. The commonality between these two is they both looking to rules in the universe. The difference is they study different rules.