The foundation of learning to think critically is the ability to recognize duality.

Duality is a universal principle (like gravity, exponential growth, or synergy) existing in multiple aspects of our life, environment, and universe. On the most basic level, duality is the existence of opposing forces in the universe.

To every action there is always opposed an equal reaction…
-Newton’s Third Law of Motion

The principle of duality runs deep into the fabric of space and time, and can be found just about everywhere.

    positive and negative
    male and female
    hot and cold
    light and dark
    right and left
    up and down
    in and out
    one and many

The essence of duality is rhythm. Most manifestations in our universe have a settling point at which they come to rest relative to their immediate surroundings. Imagine a resting pendulum, pointing straight down. If you were to lift the pendulum along its axis to 90 degrees and drop it, it would swing to the other side, and begin oscillating back and forth until it settled again, pointing straight down.

Now, imagine how this idea of rhythm permeates almost every aspect of our universe:

    At some point, the earth was set in motion spinning on its axis. The result for us was the manifestation of the rhythm between day and night.

    The earth orbits around the sun, producing the rhythm between the seasons.

    The moon orbits around the earth, tugging on our oceans. The result is the rocking motion of the tides.

    The physical rhythms of the earth have created the biological rhythms of sleep and awake, migration, mating patterns, and life and death.

What’s both amazing and beautiful is that duality exists from the smallest particles in quantum physics to the most complex and intangible manifestations, like human personality and geopolitics. From matter and antimatter, to right brain and left, to democrat and republican; duality shows us that it is deeply grounded in our universe.

More Examples

    Quantum Physics

    From the paradigm of quantum physics, experiments to discover the nature of light and energy have produced contradictory results. Sometimes energy behaves as a particle, and sometimes it behaves as a wave. The truth about energy is not yet known, but a common perception of energy is that it has a dual nature.


    From the paradigm of sociology, people tend to divide themselves into opposites: republican or democrat, business-like or creative, conformists or anti-conformist, religious or scientific, logical or emotional, capitalist or socialist, or masculine or feminine, rich or poor, criminal or upstanding citizen, just to name a few. Interestingly enough, each side believes wholeheartedly that they are right.


    From the paradigm of psychology, our emotions oscillate between happy and sad, we have both creative and logical ways of thinking (although we may prefer one over the other), we form our personalities and competencies through both nature and nurture, we might make decision based on either emotions or logic, or we might struggle with feelings of both confidence and doubt.


    From the paradigm of philosophy, duality is essential for existence. Life cannot exist without death, nor good without bad, nor male without female. Ultimately, we cannot even know who we are unless we know who we are not.

    It’s worth noting that some philosophers believe that duality is ultimately an illusion, and instead everything and everyone are manifestations of the same unified energy. In this school of thought, any separation that we experience is only created in our own heads.

    That very well may be true, but this discussion will focus on the world as we know it (or, at least, as we believe to know it.)

Duality is Not the Same as Dualism

Don’t confuse duality with dualism. While duality describes opposing forces, dualism (as defined by William Perry in his study of intellectual and ethical development of college students) describes a stage when people see the world in terms of black and white.

At first it can be hard to discern between the two, but it’s easier when you consider that dualism is part of a duality itself. The opposite of a dualistic way of thinking is relativism. Read Become a Critical Thinker for more on Perry.

What Does All of This Mean?

Theoretical physics and philosophy aside, you can use the principle of duality to help you make sense of real life situations. Any time I need to analyze a debate or issue, the first thing I do is search for the hidden duality. Once I have identified the opposing forces that are in play, I can better evaluate the issue and establish my own position.


The easiest place to spot dualities is in politics, although most people can’t see it. There is an obvious polarity between the left and the right. Each side believes themselves to be right, but how can both sides be right? Doesn’t one have to be wrong? One side must be smart and the other dumb, right?

It’s not that simple. To believe that you are right and that everyone else is wrong is a very dualistic way of thinking. It takes a critical thinker to see that two people can be on opposite sides of the spectrum and both be right within their own paradigms.

Left and Right Sides of the Brain

Everyone has heard about the differences between the right and left brain. The concept was popularized in 80’s, when I became fascinated with it after reading a book called Drawing on the Right Side of the Brain. The field of Neuropsychology is much more complex today than left and right, but it is still useful to recognize the duality that exists in our own brains.

The typical description of “right brain thinking” is creative, timeless, visionary, and figurative. “Left brain thinking” is usually described as logical, organized, categorized, and literal. You probably know people who fit each of these descriptions. It’s easy to label people as either “left brained” or “right brained,” but it’s important to know that all of us have two sides to our brains.

Since the brain acts just like a muscle, one side of your brain may be stronger than the other because it has been exercised more. That doesn’t mean that you lack the other side. You just favor one over the other.

By studying the differences between these two distinctly different ways of thinking, you can start to understand why you “click” with some people, but clash with others. You can learn which brain muscles need work to help increase your overall effectiveness. You can learn to see the world in two very different ways.

Rhythm of Life

It can also be very useful to recognize the natural rhythms and oscillations in your life. Humans have a tendency to swing like a pendulum between happy and sad, energetic and awake, euphoric and panicked, or excited and unmotivated.

To manage your own natural rhythms, it’s important to focus on stress and recovery. Read The Power of Full Engagement for more on energy management.

It’s also useful to learn the rhythms of those around you. Your husband or wife may oscillate emotionally. Some people’s emotions have greater extremes than others. If you know this ahead of time, you’ll know not to panic when your spouse is panicked. If it’s part of his or her emotional rhythm, it will be over before you know it.

Learn the Concept of Paradigm

Before you can understand the concept of duality, you have to be able to see things from different paradigms. To do so means to put yourself in someone else’s shoes and understand why they think the way they do.

When you truly understand paradigms, you will have a great respect for all human beings because you will be able to see things from their perspective. Everyone does what they think is right from their own perspective.


The thing to take away from the principle of duality is that there are different ways of thinking, and not to get stuck thinking you are right in one way without considering the other. The first step is to realize that there is another side. The next step is to use critical thinking to decide what you believe. By truly internalizing all aspects of the issue, and realizing that each side is “right” from their perspective, you will find your place not somewhere in between, but above.