In his treatise “Ars Medica”, Galen sets out the general principles of pathology and summarizes his views on the main challenges faced by the physician in daily practice. Continuing to develop and support the ideas of Hippocrates, who criticized the doctrine of “permanent illness”, Galen argued against the followers of this doctrine, consistently upholding the principle of teleology. Attempting to justify his viewpoint, he referred to the idea of homoeomeries as set out in his theoretical interpretation.