The Merriam Webster Dictionary defines holism as a theory that the universe and especially living nature is correctly seen in terms of interacting wholes (as of living organisms) that are more than the mere sum of elementary particles.
Dictionary.com defines holism as one of a number of methodological theses holding that the significance of the parts can only be understood in terms of their contribution to the significance of the whole and that the latter must therefore be epistemologically prior.
Philosophybasics.com describes holism in general terms (whether in science, sociology, economics, linguistics or philosophy) as the idea that all the properties of a given system cannot be determined or explained by its component parts alone, but the system as a whole determines in an important way how the parts behave.
So... according to these definitions, the idea of holism is that the sum of the parts is greater than the whole. The parts can only be understood in relation to the whole. And the whole comes before the parts and influences them.
In homeopathy, this can be thought of as the whole is in the parts and the parts are in the whole. The parts, (the mind, the big toe, the left lung, etc.), can be thought of as musical instruments. The person is the orchestra. One trumpet, or one lung, does not an orchestra make. The orchestra is a group of instruments playing together. Every instrument in the orchestra plays the same song or it’s just a discordant cacophony of notes - mass chaos! A person can continue to live for some time a bit out of tune in a state of imbalance but not in a state of mass chaos.
On a practical level, utilizing this idea of holism, the classical homeopath endeavors to understand the person by thoroughly investigating and understanding the expression of symptoms in the parts (instruments). Each person (orchestra) plays a certain song. We endeavor to understand homeopathic remedies by learning the many symptoms they can produce. Each remedy plays a certain song. The homeopath listens deeply to hear this music when taking a case. Then, following the law of similars, the remedy closest to the song being played by the person is prescribed.
For example the homeopathic remedy Rhus Tox, made from the poison ivy plant, is a common remedy utilized by self prescribers for joint pains. Looking more closely at the joint pains in this remedy's song we will see that they are a bit like a creaky hinge. That pain and stiffness in the knee is felt most intensely at the beginning of motion (standing up, taking the first few steps, etc.) and then eases as motion continues. This is the song being played by the knee. When asked questions a person in this remedy state may provide one syllable answers for a while and then gradually be more forthcoming as the interview progresses. Here is the same song in the mind that was being played in the knee - stiff on beginning motion, easing with continued motion. Two parts (instruments) playing the song of the whole person (orchestra). The parts in the whole and the whole in the parts.
If you'd like to explore this idea in homeopathy a bit further, I'd be happy to share a personal example with you of the parts in the whole and the whole in the parts. Please email your request to: email@example.com