Conventional chemistry has no answer to either the secret of medicinal value of high potency (above 12c) homoeopathic medicines or how they can be identified, that is, differentiated from one another. Original medicinal substance being diluted away these are chemical-free medicines. This gives leverage to skeptics to brand cures by such medicines as placebo effect or mental cure. This article shows major contradictions in their hypothesis. Thereafter, as a logical derivation it arrives at the structural model: A substance is to be recognized as a medicine if it has the capability of curing disease(s) while its medicinal property is to be attributed to molecular structure of vehicle like water or of distinct chemical substance when it exists. It is a shift of focus from chemical formula to physical structure. Several works are cited to show that the no-chemical homoeopathic medicines have water structures. Structure, be it of crude medicinal substance or of molecular structure of water vehicle, plays the predominant role throughout the potency range. So, structures give us the generalized understanding of medicines. The article also shows that there is a link between structure, medicinal value and biological effect.