One of the core concepts of homeopathy is Vital Force. It is a life force, the energy force within the physical body that protects the person from harmful agents. Vital Force animates the body and keeps it in harmony while adjusting to the disruptive changes. There are similar concepts to Vital Force. In Chinese philosophy Chi (Qi) refers to internal power, vital life energy. A more familiar concept is the immune system that promotes well-being of the body or defense mechanisms that keep the body from illness.
Samuel Hahnemann explained the concept of Vital Force in Organon of Medicine, 6th ed., Aphorism 9:
“In the healthy human state, the spirit-like life force (autocracy) that enlivens the material organism as dynamis, governs without and keeps all parts of the organism in admirable, harmonious vital operation, as regards both feelings and functions, so that our indwelling, rational spirit can freely avail itself of this living, healthy instrument for the higher purposes of our existence”