A Definition of "Spirit"
There is a deep lack of clarity in our society when it comes to being able to explain "spirit" in a totally satisfying way. It doesn't have to be this way as it's merely a matter of not having the right information. Indeed, it can be explained in detail with ease. This isn't to say that spiritual realization is an easy accomplishment because it's not. However, understanding it in a theoretical way, and having access to a detailed explanation should not be so hard to track down.
A good theoretical understanding can save us a lot of time, energy, headache. It can also prevent us from giving our power away to spiritual authorities that may have spiritual experience, but don't have clarity in understanding. There can be profoundly enlightened teachers who cannot describe how they got there. It's important to know that it's possible to experience spirit, but not fully understand what it is.
The Three Centers of Perception: Mind, Heart, and Belly
It's first very helpful to understand that spirit, or our spiritual nature, can be experienced and perceived differently through our different perceptual capacities. Our main centers of perception exist in our mind, our heart, and our body. We can call this the "head center", the "heart center", and the "belly center"(or the body/instinctual center). A fourth center, which is a nonphysical center of perception, can open up when these three bodily centers are aligned and integrated. In all of the centers, spirit is experienced as an existential presence: a special quality of experience that is different from normal thoughts, feelings, and sensations.
When spirit pervades the head center, it is experienced through the head center, as "mind qualities" of spirit, such as awareness, spaciousness, peacefulness, clarity, knowing, and so on. This center of perception represents the spiritual capacity of knowing and seeing.
When spirit pervades the heart center, it is experienced through the lens of the heart center as "heart qualities" of spirit, such as love, compassion, forgiveness, joy, fulfillment, and so on. This center of perception represents the spiritual capacity of feeling, tasting, and smelling.
When spirit permeates the belly center, it is experienced in and through the body as a palpable and tangible substance - that is, "body or physical qualities". Our spiritual nature itself has a mind, a heart, and a body. The body of spirit has physical characteristics, such as density, viscosity, texture, volume, warmth, and shape. In other words, through this particular center, our spiritual nature possesses kind of materiality. This substance can be experienced in a literal way as a liquid substance with qualities similar to the qualities of physical liquids.
The spiritual substance can be experienced as having the consistency and taste of honey, milk, butter, oil, syrup, nectar, water, and much more; that is, different kinds of substances. Spirit can also be experienced in the "solid state", having the consistency of a physical diamond, pearl, a brick of gold, or even a mountain. In its 'vaporous or gaseous state", spirit can be experienced as fire, fragrance, a subtle atmosphere, or subtle rain. This center of perception represents the capacity for "touching spirit".
Particular Usefulness of the Bodily Substance
For the skeptical parts of us, there's no other option than to experience this phenomenon directly for ourselves. If one reads classic spiritual literature, it is easy to find examples of the substantial nature of presence, but not in a way in which it is highly emphasized and illuminated as such. Of all of the spiritual lineages that I've encountered and studied, there are only two that especially highlight, and spell out in absolutely clear terms, the significance of the bodily experience of spirit: these are the teachings of George I. Gurdjieff, a 20th century Armenian spiritual teacher, and the Diamond Approach of A.H. Almaas. Both traditions emphasize an extremely refined development and sensitization of the body, and the capacity for experiencing our body sensations. Being fully in touch with our body makes the perception of this subtle experience possible.
The belly center, and the experience of spirit as a subtle substance, is the least known, understood, believed, and experienced form of spirit. This is tragic because, of all of the centers, spirit is experienced most tangibly, palpably, clearly, and fully, in the body. In terms of its usefulness on the journey, it is the one center that can completely eliminate any kind of doubt for those who are naturally skeptical or scientific. Our spiritual nature becomes no longer airy, wispy, or a fleeting experience, but an obvious, in-your-face, living substance in our bodies, and an experience that can become permanent and enduring.
Experiencing our spiritual presence in this form is also extremely useful if we want to live our realization in the middle of our busy world, and to bring it into our everyday functioning. Spiritual presence is much easier to contact in conditions that are quiet and secluded from the world, such as in passive meditation in our special meditation spot, or in a monastery. These kinds of conditions are much more conducive to the perception of subtle experience. However, when we're operating in this fast-paced world, we require a more substantial, obvious, and "louder" experience of our spiritual presence as a means to stay focused and close to it when an infinite army of external forces continually pull our attention away. Because it's so easy for our attention to get lost in our daily activity, we need our presence and our attention to more and more to be experienced as an equally solid force in its own right; to resist becoming mired internal and external influences.
The Lost Knowledge of the Spiritual Traditions of Humanity
In terms of why this bodily experience of presnce is less known, we can point to a few reasons: first, it is rarely mentioned as noteworthy phenomenon in spiritual literature, or in clear and plain language. For example, we might be able to relate to the terminology of experiencing the "presence of God". But what is the presence of God? How do we know that God is present? What is God made out of? What is the stuff of God, of Spirit?
Second, it is often the case that if it is mentioned in spiritual literate, the language is usually taken by the reader to be metaphorical only, rather than literal. It is indeed rare for skeptics to be open the possibility of this phenomenon. The last reason for why this knowledge is less knwn that I'll mention - and the most devastating to absorb - is that most people don't really want it, don't really care about it, or value it. This is a tremendous loss for humanity because it could bring a deeper realization, actualization, and embodiment, of spiritual power on Earth.
For detailed reading on this topic, the academic dissertation of Igor Giusti, PhD, documents seven major spiritual traditions that utilize the knowledge of spirit as a literal substance as an indispensable means for spiritual liberation and self-realization. These include: Theravada Buddhism, Vajrayana Buddhism, the spiritual work of the Carmelite Nun, St. Theresa of Avila, the Diamond Approach, the Jewish mystical tradition of the Zohar, and the work of Sri Aurobindo, a 20th century spiritual teacher in the Indian Tradition.
To give examples, spiritual terms such as: the "Living Water" (Christianity), "Wine" (Islamic Sufism), "land flowing with Milk and Honey" (Judaism), "Amata/the Deathless Nectar" (Theravada Buddhism), "Nectar/Amrita/Bodhicitta/Dutsi", (Vajrayana Buddhism), "Sweet/Heavenly Dew" (Taoism/Zen Buddhism), "Soma"(Hinduism), and "Ambrosia/Mana"(Greece), all point to the substantial and literal existence spirit. The vast majority of humanity believes that these terms are all but metaphorical. But I ask: metaphors for what? If we only take these terms metaphorically, and not as literal descriptions of a real spiritual phenomenon, we can miss out on recognizing this elusive substance when it naturally arises in us, or hold onto the belief that spirituality is mysterious and hard to describe - or not meant to be described at all.
After the Discovery of Essential Substance
We can see that our spiritual nature is subtle "matter", that is, a subtle kind of "material" substance, which is an explicitly confirmed phenomenon in many spiritual traditions. If we can verify this subtle phenomenon in ourselves, which means to experience our presence in any form - through any of the three perceptual centers - we have found our true inner being. Presence is an alive and subtle substance/existence that is simultaneously our inner being. It is the felt experience of our being. Any direct awareness of presence is a true vehicle, and the actual means, for spiritual realization. It will bring us clearly and continuously deeper into the very body of inner reality, the abode of spirit. This is not a metaphorical doorway, but an actual one, for those that are adventurers in consciousness.