It is what opposes that helps Fragment 8
Couples are wholes and not wholes, what agrees and what disagrees, the concordant and the discordant... Fragment 10 (my translation)
God is day and night, winter and summer, war and peace, surfeit and hunger. Fragment 67
And it is the same thing in us that is quick and dead, awake and asleep, young and old. Fragment 88
Our perception of reality is fundamentally dual. We perceive contrasts: light and darkness, sound and silence, close and far, what helps us and what threatens us. Change is the stuff experience consists of. The perception of something unchanging gets filtered out from the field of attention as useless for survival. And change is essentially dual, it has a before and an after, what is and what becomes.
The most fundamental duality is probably that which is embodied in the nature of experiencing itself, the duality of subject and object, the perceived and the perceiver, I and not I, I and thou.
The original two is reflected like in a house of mirrors in innumerable dualities: day and night, good and evil, young and old, yin and yang, God and the Devil, and even whole and not whole, as Heraclitus points out, the one and the many, the one and the dual.
Because the other half of the dual is the one. The two do not really exist as autonomous realities. As much as they are opposite they are complementary, they are two sides of one coin, they exist together, they arise together, they can only be understood together.
An interesting perspective on the complementarity of duality and non-duality is Iain McGilchrist's notion of the two halves of the brain, which in this series we will meet in the presentation of Mark Vernon. The brain hemispheres correspond to two essentially different modes of processing information, which we could describe as the dual (left hemisphere) and the non-dual (right hemisphere). The first is analytical, it distinguishes and separates, it focuses on differences, it perceives me and other, it is centered on my survival and sees the world as conisting of separate objects. The second one attends to totality, wholeness, the overall Gestalt, the pattern that connects, the oneness of this miraculous existence we inhabit.
In this perspective the brain is dual, but that duality is only one perspective, the analytical one, while in the other perspective there is only the undivided wholeness of being, within which the illusion of separation arises, the illusion of a world consisting of separate things, of separate objects.
This complementary understanding of duality is also a key feature of quantum physics. A notion that sharply distnguishes the quantum from the classical world is the notion of complementary observables, an example of which are the position and momentum (the product of mass times velocity) of a particle. These two are both needed to describe the motion of the particle, but cannot be measured together: when you measure one of them with a certain degree of precision you introduce a corresponding degree of uncertainty in the measure of the other one. Quantum reality is slippery, it is like a balloon, when you squeeze it one way it expands the other way.
That is the gist of Heisenberg's uncertainty principle. Another formulation of quantum complementarity is the dual mode of wave and particle: an observation apt to measure the particle properties of a quantum system loses sight of the wave properties and viceversa, if I focus on the wave properties I loose sight of the particle. Which is it then? Both or neither, duality is complementarity.
Niels Bohr, who introduced the notion of complementarity in physics, was well aware that its range of applicability is much wider. He is known to have said "The opposite of a profound truth may well be another profound truth". And Jung, another master of complementarity, talking about the chinese understanding of polarities, said:
The Chinese have never failed to recognize the paradoxes and the polarity inherent in what is alive. The opposites always balanced one another - a sign of high culture. One-sidedness, though it lends momentum, is a mark of barbarism.
Quite obviously, the Chinese owes the finding of this path to the fact that he was never able to force the opposites in human nature so far apart that all conscious connection between them was lost. The Chinese has such an all-inclusive consciousness because, as in the case of primitive mentality, the yea and the nay have remained in their original proximity...
A Chinese master for whom the yea and the nay have remained in their original proximity is certainly Laozi. In the second stanza of his Daodejing he says:
When in the world all appreciate beauty as beauty,
then ugliness is already there;
when all appreciate good as good,
then bad is already there.
Therefore being and non-being generate each other,
difficult and easy complete each other,
long and short define each other...
And duality as a matter of fact of experiencing is reflected in religions and mythologies: in the Indian Upanishads Brahman, the Creator, gets bored with his/her eternal unchanging perfection and absolute completion and creates the world for a little diversion, for experiencing otherness, for enjoying the play of the bull and the cow.
In the West the dualistic view has largely prevailed, and it has taken its strongest form in the monotheistic religions, with the sharp separation of good and evil, God and the Devil, and the corresponding split between mind and matter, whose consequences we are witnessing everyday in our disregard for life in all its forms.
Yet also in the West there is a long tradition of non-dualist thinking. A prominent representative of that tradition is Baruch Spinoza, whose remarkable formula Deus sive Natura is a beautiful synthesis of the dual and the non-dual. God is Nature and Nature is God, these two are one, and yet this one is the many, it is the fantastic abundance of form...
When we mention form the thought flies to what may well be the most radical formulation of opposition/complementarity in human thought, the Heart Sutra of Buddhist tradition:
Therefore, Sariputra, form is emptiness and the very emptiness is form; emptiness does not differ from form, form does not differ from emptiness; whatever is form, that is emptiness, whatever is emptiness, that is form...
In this series of talks we'll explore duality and non-duality from a variety of perspectives, too many really to enumerate exhaustively. Let me just give you some pointers, a taste of what is to come.
A very special feature of this series is Mark Vernon series within the series, over four Sundays exploring the specificities of the mystical path in the West as embodied in four representative figures: Plato, Dante, William Blake and our dear friend Iain McGilchrist.
On the Saturdays various presenters will alternate.
In this first Saturday my friend Andrew Fellows, Jungian analyst, physicists and ecologist, his student Anjali D'sousa, who recently graduated from ISAP Jungian training, and myself will hold a conversation on duality and non-duality in East and West, taking advantage of Anjali's experience of India and of Eastern mystical traditions.
The following Saturday film maker Jena Axelrod and the physicist and mathematician Basil Hiley, student and collaborator of David Bohm, will look at a nondual perspective on the universe based on the notion of quantum potential, a concept introduced by David Bohm and considerably developed by Basil Hiley. Jena will make sure to keep Basil on earth when he tends to fly away on one of his mathematical astral travels.
Connecting the Actuality of Things in Space-Time to the Reality of Possibility in QuantumLand will be the task of quantum physicist Ruth Kastner and neuroscientist and philosopher Gary Goldberg. They will offer us a yin view of reality based on the transactional interpretation of quantum physics, in which all interactions involve an exchange of active information carried by waves travelling forward and backward in time.
David Schrum, another friend and student of David Bohm, will guide us on a mystical voyage inspired by the Bohm's own journey of self enquiry, a journey that is away from nothing but, rather, is into what is, a journey beyond words and concepts and their dualities, a journey to the 'farthest shore' that is ultimately recognized to be this very shore, the very earth we are standing on.
The Jungian analyst Marc Saban will introduce us to Jung's two personalities and to how the tension and dynamics between them informs the basic principles behind the development of Jung’s psychological model and indeed Jung’s entire mature psychology.
On the last day of the series I will accompany my friend Mauro Bergonzi, a teacher and practitioner of Advaita Vedanta, in an exploration of various facets of non-duality. In this tradition the opposing terms ‘consciousness’ and ‘world’ are viewed as two different conceptual descriptions (in terms of the ‘first’ or of the ‘third’ person perspective) of one and the same indivisible reality.
And with this it is my pleasure to pass on the talking stick to my companions today, Anjali and Andrew.
 Richard Wilhelm, The Secret of the Golden Flower, Arkana Penguin Books, London and New York, 1984, p. 85.