Often we pay so much attention to learning the physical postures and applications in T'ai Chi that we forget about how we learn. We learn best by using our whole bodies.
I find that when I am trying to figure things out, like a new posture, my focus can become narrow. This is what most of us were taught in school; paying close attention meant shutting down our awareness into a narrow, concentrated point. This is useful in some cases, like solving a maths problem, but counterproductive when learning T'ai Chi. When I catch myself in 'narrow focus' , I soften and widen my vision.
When our vision de-converges our plain of focus remains the same but our view widens. Even without moving our eyes we take in more visual information around us. This peripheral vision produces a much different type of understanding, one that is broad and holistic and very conducive to learning.
This is not to say that narrow, or converged, vision is not useful in T'ai Chi. When we want to analyse and perfect a posture or when we want to express energy in an application, narrow focused vision is best. For example , the energy delivered in an application can be greatly increased by using our eyes .
Beginners often look down as they yield and this dissipates their energy into the ground . By simply lifting their gaze, the application becomes 100% more effective.