Most Taoist lineages -- and in particular the Shangqing lineage -- utilize visualization practice as one technique for restoring health and balance in the bodymind; supporting alignment with more and more subtle realms of being; and, eventually, dissolving into / merging with the Tao.
The objects visualized vary greatly. For instance: In the Inner Smile practice, we visualize smile-energy penetrating and revitalizing our internal organs. In the Moon On Lake practice, we visualize a lake upon whose surface is reflected a beautiful moon -- all within the space of our heart-center. In Holding Heaven In The Palm Of Your Hand, we visualize the energy of the sun and moon and all the stars flowing into the palm of our hand, and then down into our lower dantian.
Whatever the object is that we are visualizing, the basic principles at play are pretty much the same. We’re using a very potent aspect of our human functioning -- the power of imagination -- in a way that supports our qigong practice. Why is this such an effective tool? There are a number of reasons ....
For one, visualization practice gives our typically-overactive conceptual mind a specifically-defined job, which tends to keep it happy and willing to participate -- instead of (largely unconsciously) wandering here and there, as it is wont to do. As we train in maintaining a clear and stable image, we are engaging in a form of meditation practice known as “shamatha with an object.” What this means is that we’re using a visualized object as a support for focusing our mind, in order then to access a state of calm abiding.
In relation to qigong practice, visualization practice utilizes and supports the foundational principle of qigong, namely: “energy follows attention.” Where we place our mental focus, there life-force energy (qi) gathers. So for instance: visualizing a golden sphere of light in our lower dantian, and gently maintaining focus on this visualized object, in that location, draws qi into the lower dantian. Visualization practice allows us to consciously direct the flow of qi, into locations within or outside of the body.
Most foundationally, working with visualized images/objects -- which are so clearly a product of our mind (our power of imagination) -- helps us to avoid the epistemological mistake typically made, when our “object” of meditation is a seemingly “external” and “material” form, viz. the assumption that the object is permanent, separate and inherently existent. Visualizing our body as a deity, for instance, is one way of challenging our habitual tendency to perceive the body as a dense, unchanging and inherently existent form; and to believe that who we are, essentially, is the body.
Though it’s still possible to concretize imagined forms (e.g., in the case of theistic gods), it’s certainly not as automatic an impulse as is our concretizing of the various “things” of the “external world.” Allowing imagined/visualized forms to inhabit the space of a seemingly-solid object is one way of gradually refining our perception, in the direction of having phenomena (i.e. the “ten-thousand things”) appear in accordance with how, in Reality, they actually are.