Continuing to discuss Taoism for the Modern Age...
Most people will be familiar with the Taoist symbol known as the taiji (even if you didn't know it was called that. By the way, that name is the first part of the Chinese martial art/exercise system called taijiquan or Tai Chi.)
It is a circle with two different colour "swirls" with a dot of the opposite colour in each swirl. It represents the union of yin and yang in the Tao. Each of these is traditionally associated with particular qualities (yin is darkness, femininity, cold, etc.; yang is light, masculinity, heat, etc.). But for philosophical purposes, it really only matters that these are opposite qualities.
In most of the western religious and philosophical tradition, dualism is the norm. Good and evil, spirit and matter, to take two obvious examples, are conceived as utterly distinct and opposing things. Once you have classified something as one or the other, it is permanently and solidly in that category.
In contrast, the Taoist approach to opposites is monistic, in that the opposites are conceived as being part of the same thing, flowing organically into one another. (Hence the opposite dot in each swirl.) The whole philosophy of the Yijing is based on this idea: yin lines change into yang ones and vice versa, the speed and ordering of the changes producing the different flows and outcomes.
The canonical model of Chinese dynastic history follows this model: an old dynasty becomes corrupt and ineffectual, and is replaced by a new, virtuous and vigorous dynasty that will ultimately succumb to the same fate (hopefully after centuries).
We see similar examples all the time in the modern world: the hot, new thing becomes tomorrow's cliche, today's hero is tomorrow's villain (and sometimes vice versa).
A major form of dualism these days is political dualism: left and right, conservative vs. liberal. Strangely, when the Left/Right metaphor originally became current, the conservatives were those who believed that the state (the king) should control everything for the common good, and the liberals were those who believed in free markets, free enterprise and individual autonomy. Today, these words tend to have the opposite associations.
The big problem with demonizing one's enemies and being so sure that your side is on the side of the angels is that it can be a little bit too easy to miss the changes in the flow. Today's liberator is tomorrow's dictator. Today's high-minded idealist is using gutter techniques to beat "the bad guys" next week.
A Taoist outlook reminds us that there are no hard lines between opposites and that these lines are always moving and shifting. Rather than clinging to certainties, it is better to keep a holistic, realistic perspective. Those who cling too vigorously to a particular "good" often end up not noticing when the thing they are clinging to has shifted over to the side of harm.
Taoism suggests that it is better to be healthy and happy in ambiguity than to be rigidly and lifelessly on the side of "the good and the right".