Taijiquan and Seeing

 "Looking and seeing are two different things. In tai chi we see without looking. When we look, we focus our gaze on some point. As we do that, there are subtle changes in our facial muscles which affect all our muscles. We see what we're looking at but miss the rest. Imagine having to deal with multiple opponents. The ideal is to see as if you're looking from behind your head so that your vision broadens. An easy way to understand it is by holding your arms at your side as if making a cross with your body. Can you see your hands with your peripheral vision? If you can, that's what your seeing should feel like. As you do that, you will notice that things get quieter and softer, more relaxed, and seem to slow down."
- Joe Eber, Facebook Post 

"Eyelids relaxed:  The eyelids should be relaxed like a curtain. As the eyelids relax, the mind is able to calm down and release the tension of the body’s muscles. The facial muscles also need to be soft and relaxed. As always, your outlook should be aware but not focused. Another reason to curtain the eyes is to hide your intention from others. In a martial arts’ sense, this is used for effective defense and offense.

Center the vision:  Set the eyes straight ahead but do not focus outward onto anything in particular. I tell my students to see, without looking; likewise to hear, without listening. By not focusing on any one thing, we cultivate awareness of all things. A centered vision helps to engage our peripheral vision so that we get a better sense of what is going on all around us. This also encourages awareness of our internal environment; our sense of feeling, balance, movement, and posture. A centered vision pertains to seeing both within and without."
-  William Ting, Essential Concepts of Tai Chi  

"What is the color of your head from the standpoint of your eyes?  You feel that you head is black, or that it has not any color at all.  Outside you see your field of vision as an oval because your two eyes act as two centers of an ellipse.  But what is beyond the field of vision?  What color is it where you can't see?  It is not black, and this is an important point; there is no color at all beyond your field of vision.  This little mental exercise gives us an idea of what is mean by the character hsüan.  Although its dictionary definition is "dark, deep, obscure," it actually refers to this kind of no color that is the color of your head - as far as your eyes are concerned.  Perhaps we could say that the invisibility of one's head, in a certain sense the lack of a head, is the secret of being alive.  To be headless, or have no head in just the same sense I am talking about, is our way of talking about the Chinese expression wu hsin, or "no mind."  As a matter of fact, if you want to see the inside of your head all you have to do is keep your eyes open, because all that you are experiencing in the external, visual field is a state of your brain."
-  Alan Watts, Swimming Headless, 1966 

Vision, Seeking, Sensations, Perceptions, Looking  By Michael P. Garofalo

Seeing, in solo Taijiquan practice, refers mostly to being visually aware of one's immediate physical environment your moving within.  With home indoor practice, that involves awareness of tripping hazards, walls, chairs, etc.  Adjustments are made accordingly.  Take in the big picture of where you are practicing - outdoors or indoors.  A wider angle of vision is preferred.

Some aspects of seeing in Taijiquan practices involve carefully looking at an imaginary opponent, your hands, or in a specific direction.  Looking is a focused kind of seeing, and the field of vision is more circumscribed.