Since homeopathic remedies come from the natural world, they can also be categorized into the kingdoms of nature, plant, animal and mineral. People who need remedies from animal sources will have different characteristics and types of symptoms from people who need remedies from mineral or plant sources. Rajan Sankaran developed this idea in his book, The Substance of Homeopathy.

It makes immediate intuitive sense that people needing plant remedies will be like plants in some way, and people needing animal remedies will be like animals, but until very recently homeopaths had not really considered that this idea could be helpful in prescribing. In clinical practice, the remedy picture was not considered to be related very much to the characteristics of the source material. A great body of knowlege has been collected about the symptom pictures of remedies and their similarities and differences, but not much work had been done on looking at this data from the point of view of the kingdoms. Farrington's Comparative Materia Medica is the best of the old homeopathic works in this area. Farrington looks at the commonalities and individual characteristics of groups of remedies like snakes, spiders, oils, milks and mineral salts. It may seem obvious, but it was something of a revelation to realize just how intimately the symptoms in a remedy's picture do correspond to the characteristics of the original substance and the common characteristics of members of its natural kingdom.

Since studying with Sankaran, we have come to believe that categorizing according to kingdom can be a very useful, if not vital, tool in finding the correct remedy for the patient. In figuring out the characteristics that we might expect from remedies in the different kingdoms, it is important to look at the characteristics of the members of each kingdom as they appear in nature. Although no one person will have all of the following characteristics, enough will often be present to identify him predominantly with one kingdom.

Think of plants. Plants vary from unicellular organisms to huge trees. The common features of plants include photosynthesis, rootedness, spreading out, various forms of reproduction and sensitivity to environmental changes. They use sunlight, oxygen, nitrogen, water, soil and other nutrients as sources of energy and life.

According to Sankaran, the basic quality of a plant is sensitivity. Plants grow, but do not move under their own power from place to place. They stay in one place and must be sensitive to the environment in order to adapt to the changes around them. Your house plants don't just get up and move when the sun moves, like your cat or dog, but they grow slowly toward the source of sunlight. Plant remedies in homeopathy are also quite sensitive, trying to adapt to changing circumstances. People who need plant remedies are often soft, sensitive, attempting to adjust to the people and environment around them. They are passive, emotional, easily hurt, changeable, and lack structure. Just as plants can spread out into the available space, absorbing what is necessary for life, these people are more diffuse by nature, wandering in thought and speech, guided by their emotions, looking for support and nurturing. They are often creative and artistic, looking to create and surround themselves with beauty, such as art and music. They are flowing, reactive, fragile, and more random in thought and speech. Their writing may look irregular, or disorganized, with rounded letters.