Noticing differences greatly assists survival… up to the point of diminishing returns, especially for a thinking animal like us. Even so, the naïve acceptance of difference as a true portrayal of reality would not have been a problem for our hunter-gatherer ancestors, given their truly down to earth circumstances.
Conversely, our naive acceptance of difference as a true portrayal of reality causes anxiety, given the less down to earth nature of civilization. Civilization, by taming the wilderness, removes many natural demands that would otherwise counterbalance anxiety. Before we know it, we become neurotic nitpickers in one way or another.
Chapter 56 proposes a way to mitigate the ‘difference bias’ that so easily swamps cognition and ramps up stress: Block the openings; Shut the doors. Blunt the sharpness; Untangle the knots; Soften the glare; Let your wheels move only along old ruts. This is known as mysterious sameness.
It helps to know where we are on the bell curve of balanced awareness, i.e. between devoting too much or too little credence to differences. As with maintaining physical balance, noticing when we near the tipping point is crucial. Chapter 64 observes, Deal with a thing while it is still nothing. That requires warily watching the mind. As chapter 71 ends, It is by being alive to difficulty that one can avoid it. The sage meets with no difficulty. It is because he is alive to it that he meets with no difficulty. The difficulty here is our inborn tendency to focus excessively on differences and seldom on similarities. That’s because noticing difference carries a much greater evolutionary / survival value for creatures living in the wild.
To top this off, desire (need + thought) exacerbates this imbalance by inducing us to gloss over differences at times, and yet make mountains out of molehills of difference at other times. Our mind and its thoughts trap us. No wonder chapter 71 cautions, Thinking that one knows will lead to difficulty.