Emptiness is also sometimes called selflessness, and it refers to the ultimate nature of how all things, including people, exist in this world. Normally we think of ourselves as existing independently from anything else. But when you examine what existing is really carefully, you might realize that whatever it is that you call “I” or “me” isn’t easy to define at all. Is your “self” in your head? You my say “this is my hand”, but who is the owner of that hand? Is it that thing we call a spirit? You were once a little kid who believed in Santa Claus. Is that you? If you had an operation or an accident which caused you to lose your memory, would you still be you? You might be able to answer some of these sorts of questions with confidence, but as you delve deeper and deeper into the question of where and what your ’self’ is, it becomes less and less clear. In fact, what we think of as our ‘self’ doesn’t exist at all. Its just a construct of our minds that makes us able to function in the conventional world. In fact, the true nature of reality is called “dependent origination”. Without an observer, the observed doesn’t exist, and without an object to be observed, the observer doesn’t exist. That is what is meant by emptiness: the true nature of reality is that objects including people, are empty of inherent existence. It’s a very subtle distinction, which takes lots of meditation and practice to really understand.

The Buddhist notion of emptiness is often misunderstood as nihilism. Unfortunately, 19th century Western philosophy has contributed much to this misconstruction. Meanwhile Western scholars have acquired enough knowledge about Buddhism to realise that this view is far from accurate. The only thing that nihilism and the teaching of emptiness can be said to have in common is a sceptical outset. While nihilism concludes that reality is unknowable, that nothing exists, that nothing meaningful can be communicated about the world, the Buddhist notion of emptiness arrives at just the opposite, namely that ultimate reality is knowable, that there is a clear-cut ontological basis for phenomena, and that we can communicate and derive useful knowledge from it about the world. Emptiness (sunyata) must not be confused with nothingness. Emptiness is not non-existence and it is not non-reality.

What is emptiness then? To understand the philosophical meaning of this term, let's look at a simple solid object, such as a cup. How is a cup empty? We usually say that a cup is empty if it does not contain any liquid or solid. This is the ordinary meaning of emptiness. But, is the cup really empty? A cup empty of liquids or solids is still full of air. To be precise, we must therefore state what the cup is empty of. Can a cup be empty of all substance? A cup in a vacuum does not contain any air, but it still contains space, light, radiation, as well as its own substance. Hence, from a physical point of view, the cup is always full of something. Yet, from the Buddhist point of view, the cup is always empty. The Buddhist understanding of emptiness is different from the physical meaning. The cup being empty means that it is devoid of inherent existence.

What is meant with non-inherent existence? Is this to say that the cup does not ultimately exist? - Not quite. - The cup exists, but like everything in this world, its existence depends on other phenomena. There is nothing in a cup that is inherent to that specific cup or to cups in general. Properties such as being hollow, spherical, cylindrical, or leak-proof are not intrinsic to cups. Other objects which are not cups have similar properties, as for example vases and glasses. The cup's properties and components are neither cups themselves nor do they imply cupness on their own. The material is not the cup. The shape is not the cup. The function is not the cup. Only all these aspects together make up the cup. Hence, we can say that for an object to be a cup we require a collection of specific conditions to exist. It depends on the combination of function, use, shape, base material, and the cup's other aspects. Only if all these conditions exist simultaneously does the mind impute cupness to the object. If one condition ceases to exist, for instance, if the cup's shape is altered by breaking it, the cup forfeits some or all of its cupness, because the object's function, its shape, as well as the imputation of cupness through perception is disrupted. The cup's existence thus depends on external circumstances. Its physical essence remains elusive.

Those readers who are familiar with the theory of ideas of the Greek philosopher Plato will notice that this is pretty much the antithesis to Plato's idealism. Plato holds that there is an ideal essence of everything, e.g. cups, tables, houses, humans, and so on. Perhaps we can give Plato some credit by assuming that the essence of cups ultimately exists in the realm of mind. After all, it is the mind that perceives properties of an object and imputes cupness onto one object and tableness onto another. It is the mind that thinks "cup" and "table". Does it follow that the mind is responsible for the existence of these objects? - Apparently, the mind does not perceive cups and tables if there is no visual and tactile sensation. And, there cannot be visual and tactile sensation if there is no physical object. The perception thus depends on the presence of sensations, which in turn relies on the presence of the physical object. This is to say that the cup's essence is not in the mind. It is neither to be found in the physical object. Obviously, its essence is neither physical nor mental. It cannot be found in the world, not in the mind, and certainly not in any heavenly realm, as Plato imagined. We must conclude that the objects of perception have therefore no inherent existence.

If this is the case for a simple object, such as a cup, then it must also apply to compound things, such as cars, houses, machines, etc. A car, for example, needs a motor, wheels, axles, gears, and many other things to work. Perhaps we should consider the difference between man-made objects, such as cups, and natural phenomena, such as earth, plants, animals, and human beings. One may argue that lack of inherent existence of objects does not imply the same for natural phenomena and beings. In case of a human being, there is a body, a mind, a character, a history of actions, habits, behaviour, and other things we can draw upon to describe a person. We can even divide these characteristics further into more fundamental properties. For example, we can analyse the mind and see that there are sensations, cognition, feelings, ideas. Or, we can analyse the brain and find that there are neurons, axons, synapses, and neurotransmitters. However, none of these constituents describe the essence of the person, the mind, or the brain. Again, the essence remains elusive.