This is a question we get a LOT. People want to know what it is. Traditionally speaking, of course, Chinese philosophers have struggled to define Qi (Chi) and end up by saying “Qi is everything, so it is undefinable.”
This doesn’t sit well with Westerners who have a pigeonhole for everything in the modern world. So rather than give you the fortune-cookie, wax-on-wax-off answers, I’m going to just give you my take as according to what the Chinese Classical texts seem to be hinting at.
First you need to know there are two types of Qi that make the discussion difficult. The main Qi most people seem to be trying to peg down is what we can call Universal Qi. Universal Qi would most easily be translated into Energy, but would also include matter, the four forces of gravity and electromagnetisim (one common citation as being Qi, but far too narrow), strong and weak, as well as the field lines that they emanate. It would include light itself, and on the other side the Darkness, which has a nature, and is not simply an absence. Universal Qi would be anything and everything that moves, which so far is … everything known because nothing is at Absolute Zero (Kelvin). So if it moves, it is made of Qi and has Qi flowing through it. This is a key point.
The other kind of Qi is what people seem to like to deem a “life force.” Of course there has not yet been found a force that makes life different from death or inanimate objects, but that’s the point. The Chinese couldn’t find it either, and so they called it Qi.
The original character for Qi was the steam coming off of rice; and has commonly also been translated as “breath.” This indicated transformation, and of course change is an important aspect of the Universe, especially life.
So this concept is perhaps useful. It’s not so much like the Force in Star Wars, (except in philosophical theory) although using one’s Qi one can do some interesting things. Qi fields, balls of heat, sensations of roving electricity, detecting presences, healing, etc… are all things readily done with some Qi Gong (Chi Kung) practice. But you won’t be lifting cars, choking people, or doing any Jedi mind tricks. You won’t be catching paper on fire.
In Chinese Medicine we don’t talk about a Force, we talk about processes of physiology. We talk about food, drink, and air, and Essence which is roughly to say DNA and marrow. We talk about blood and how it is the “mother of Qi” but the Qi moves the blood.
We talk about Yang Qi, which warms and moves, and Yin Qi which nourishes and moistens and anchors. We talk about Ying Qi which is like plasma working with Wei Qi which is like your immune system and vascular system.
We talk about Ancestor’s Qi which comes from the realm of the spirit and makes us whole, and about Turbid Qi which we flush out of us old thoughts, emotions, food, and urine.
All of these Qi describe activity in the body.
So basically the Chinese found a quick, but practical, way to describe the same body that biomedicine talks about. Who has time to remember which macro and micronutrients one eats… and which ones are deficient? Who knows every minute detail about the latest research on dieting and what phytochemicals attach to which antioxidants… yadda yadda?
The Chinese had not the technical skill, nor the interest. They just said, “That’s Qi.”
So although trying to fit Qi into our western world is sometimes like a square peg in a round hole, the reality is it is a complete way of looking at health and life through simplicity and practicality. One need not explain it, just feel it and use it. The first time you do, you won’t forget after that. Pretty soon you’ll be interested in what it is from a deeper perspective.
Speaking of a deeper perspective, I mentioned that the Universe is moving all the time. Even the solid objects around you are mostly empty space with just field lines emanating from vibrating subatomic particle-waves.
So if the Universe is like our body… and God is the mind to our Universe… then Qi would be everything flowing through the known Universe, or roughly speaking, ‘God’s nervous system.’ Pretty profound, eh? The Chinese found it so profound they just called that Dao and moved on. And that’s the best thing to do with Qi: move it along. That’s how the Qi Ji (machine) – our body – stays healthy and growing throughout life. Pleasant travels.