Modern science grew out of the idea that the universe is comprised of independent parts, and a complex system can be reduced to these parts without loss of completeness. The independence of parts became the basis of reductionism―the idea that the whole is simply a linear sum of parts. Sometimes, this reduction fails, and then it becomes necessary to postulate that the parts are indeed interdependent. The reason for this interdependence, however, has not been very apparent. I will describe the reasons in this post, and connect them to the “systems approach” which views a system as a collection of interrelated parts rather than mutually independent parts.