There are things which we, as humans, do because we have been conditioned to do them since the time of our earliest memories as a child; we take these instilled behaviors for granted, without ever questioning them. These are the conventional aspects of our lives. For example, we take for granted that the objects we see (including our self) exist in reality as they appear to us.

Some people go beyond taking the appearances for granted, and ask such questions as: If the phenomena in the universe are real, why do they not remain lastingly unchanged?; Considering the current condition of phenomena in the universe, is this the ultimate condition?

So, conventionally we take it for granted that the things in the universe are real, and yet we can ask if what we assume to be real is the actual condition of reality ultimately.

Through logical reasoning, the sunyata masters (for example Nagarjuna, Aryadeva, Chandrakirti, Shantideva, etc.) have determined that emptiness is the ultimate, fundamental reality; and that therefore all the phenomena which appear to us are actually empty of reality.

The universe and the contents of its phenomena are, in the context of reality, unreal. This is why Buddha proclaimed “Form is emptiness, emptiness is form”. All the things we presume are true conventionally, are true only in the ultimate sense of their emptiness. And yet, what makes this conclusion paradoxical is that if we consider emptiness as an alternate of any form it imbues, this emptiness—as with any other form—must also be empty of reality.

In other words, if emptiness is considered as any other thing is conventionally considered, it too is simply another thing to which “unreal” applies.

Since emptiness is not simply another entity to be contrasted to the entity of form (which it does imbue), it does not arise separately from form; when form arises, it arises as emptiness. Emptiness is not “added on”, as something apart from form. “Form is emptiness. Emptiness is form.”

Likewise, when a form ceases, emptiness ceases. Emptiness does not have a form; apart from its existence as form, it does not exist—emptiness is empty of reality.

So, while we may speak of emptiness as the ultimate condition, total and complete emptiness is not in a position to be in any kind of “condition”, ultimate or otherwise. Emptiness has to be utterly empty.

We speak, in conventional terms, of emptiness “existing” as form exists. (Yet form does not exist, because it is empty of reality.)

But apart from conventionally, emptiness does not exist in any way that we assume phenomena exist.

In other words, emptiness can be described as existing and not existing. (Forms, in truth, have never existed because they have always been empty of reality, or existence.)

The significant importance of the work of the sunyata teachers is that it makes clear to us that not anything (including emptiness) actually exists as it appears—and that, of course, includes us. An unreal person—empty of reality from beginning to end—looks out on an unreal universe.

In the words of perennial sages, not anything has ever actually happened: arising, decaying and subsiding are all fictional appearances.

The above explanation can help make clear some of the following excerpts by Geshe Tashi Tsering:

In Buddhist philosophy, when we speak of how things exist and how we perceive they exist, we are talking about two truths: ultimate truth and conventional, or relative, truth… Our knowledge of emptiness is itself a conventional truth… Although it may seem strange that emptiness can have a conventional truth nature as well as an ultimate truth nature, it must be understood that emptiness can have a conventional ‘truth’ nature, not that it is a conventional truth….

Beyond the conventional causal dependencies that rule our lives, there is a fundamental mode of existence that all things and events share; that is ultimate truth…. Therefore, say the Prasangikas, on a conventional level, external objects ‘exist.’ For Prasangikas, to apprehend something as a truth is to apprehend it as it actually exists….

It is also a truth because the way it exists and the way it appears to the mind of a superior being—one able to realize emptiness directly—are the same…. But to exist conventionally is to exist dependent on causes and conditions. That empty interdependence is the mode of existence of all things, including all conventional truths and ultimate truths….

The two truths are also the same entity in that they have the same duration. The conventional truth and ultimate truth of a phenomenon arise, abide, and disintegrate at the same time. There is no sequence in which, for example, a conventional truth is generated and then, as a result of that, at a later time, an ultimate truth is generated…. It’s not that emptiness is tacked on to the object as something separate. The object is the same…. One of the consequences of an object’s conventional side and ultimate side being the same entity is that the buddhas do indeed perceive these two natures simultaneously in one object…. He or she can see that things do not exist in the way they appear.

The aspect found by such a mind is called an ultimate truth, or emptiness, or thusness…. Emptiness is a nonaffirming negation; it negates true existence without presuming something else positive in its place…. EMPTINESS (Skt. shunyata): the ultimate nature of all phenomena, which is their lack of any inherent or independent existence…. Nothing exists ultimately.

— Relative Truth, Ultimate Truth