Wholeness is regarded as the sum of the parts, a quantity of all its parts. The whole human being is the sum of its parts. As we go down the holarchy (holon levels) we can say it first is the sum of organs (including limbs), then all the tissues, all the cells or on an even lower holon level the sum of all its molecules or even atoms.

At a subatomic level looking at the sum of the fermions and bosons we are confronted with some challenges like virtual particles and the appearance and disappearance of short lived particles. Here it is better to perceive the whole as a field of energy. Where the particle is just an expression of this coherent human field. (Read more about The atom from solid balls to sparkling ghosts)

At the moment a person dies, all parts are still there and many functions continue. At a closer look there is a unity a coherence that rapidly diminishes and as it diminishes we see degeneration.

If a person believes only in evolution, the human being is regarded as an expression of selection and replication more or less by luck. And luckily that expresses the higher more advanced organization of the advance chemistry in the brain giving us thinking and feelings.

If you like me believe in involution too, there is a higher aspect that not only incarnates into the human being, but also organizes all in a coherent unity. This interconnecting principles is what is there in addition to all the parts. The field of the subatomic particles, is a coherent field and it gets different levels of organization as life evolves.

In esoteric teaching like Anthroposophy, Theosophy or the teaching of Martinius, Deunov, Omraam and many others this coherence principle or vital body or human soul has many levels.

Closest to the physical body we have the chemical ether that keeps the physical body with its cells and tissues in a coherent structure. The next vital or life ether keeps the functions necessary for living just at the most basic level. Vegetating like a plant in a state of coma.
To rise from that we need the sensory ether that facilitates the bridge with the higher astral body to the senses and then the memory ether which takes part in storing our memory as well as connecting the brain and mental function to the higher mental body. This completes the four levels of the etheric body that we share as coherence principle with both animals and plants. Minerals do not have an etheric body.

The next or astral body creates a coherence on the level of the organs, emotions, digestion, locomotion and senses. We share an astral principle of coherence with animals.

The mental body is unique to humans and at a very early stage in a few highly evolved animals. It gives an awareness of self and an increasing degree of cognitive skills.

When you want to understand yourself, “know thyself” as it says above the entrance of the temple in Delphi or when a therapist wants to perceive the whole client we have to discern between wholeness and unity.

Details and facts can add to the wholeness but details can reach a level of quantity that becomes chaotic or overwhelming. By seeing a theme running through the wholeness one can start to perceive the unity at higher and higher levels of coherence. One starts to see the particular modus operandi, taste, colour or quality that runs through all parts of the human economy. The wholeness of each individual is individual and can be perceived as a unified theme.

Wholeness is about quantity and unity is about quality. You need a certain quantity of information to perceive the unity. As you go deeper and deeper into a case the wholeness expands and the unity creates a coherence in more and more of the quantity. Finding a unifying principle is not a proof that you have reached the top or bottom. Until all new information also aligns with the unifying theme it might be a partial unity or just a part of the wholeness you perceive as unified.
In the illustration below the smaller holons represented by smaller cones each have a unity represented by its peak or top. They all connect in a higher holon with a higher coherence into a new unifying principle.

This is also illustrates the higher levels of coherence when life evolves from plant, to fungi, animal and human levels.

The degree of harmony between holons at different levels I call holonity. When all organs are in high degree of holonity with the human body it is a sign of harmony and health.

When you start to work with perceiving and conceptualizing a unity in clients you will see that a unity is always easiest understood through its polarity.
Looking for opposites can be as valuable as looking for similars when you want to perceive a theme or core in a client or yourself.

The unity can only be experienced when you unite with it, but to perceive it you need to see the polarity behind its manifestation.
Read more about the relation of unity and polarity here.