"There are as many types of non-dualities as there are dualities." - David R. Loy
Each practice polarity is felt as an internal tension. We typically try and resolve these tensions by settling on one side, or the other, of the poles. This never works, because the polar nature of reality doesn't conform to our wishes. Practitioners will also often find themselves flipping between polarities, or like with the proverbial angel on one shoulder and devil on the other, will find an internal dialogue/war going on between the two sides. It often feels like these polarities are tearing us apart.
The practice of the Buddhist Middle Way is to hold both sides of any practice polarity in attention at once. When we can hold both extremes of each polarity in attention simultaneously, and let them do their natural oscillating thing, then we have become aware of the transpolar, or non-dual, nature of this polarity. It no longer polarizes us in the same way as before, as we've learned how to simultaneously include both extremes, not just conceptually, but in the full presence of our loving awareness. We can now see the pros and cons of both extremes, and the way that these seeming opposites complete one another and us.