"Mahamudra" is a Sanskrit word meaning "great seal" and refers to the nature of all phenomena. Just as a wax seal is stamped on legal documents to authenticate their signature, likewise the nature of reality is figuratively stamped upon everything as a guarantee that nothing exists in a fantasized, impossible way. The fact that everything is devoid of existing in any impossible manner thus validates that things actually exist.

Mahamudra also refers to sophisticated Buddhist systems of meditation and practice to realize this great sealing nature. The distinctive characteristic of these methods is to see this nature by focusing on mind itself and discovering the relationship between mind and reality. When our mind confuses reality with fantasy, we produce problems for ourselves. Furthermore, when our mind gives rise to an appearance of others in a way that does not correspond to their reality, we are unable to know them accurately in order to be of most help. Understanding the intimate relation between mind and reality, therefore, is essential for achieving both liberation and enlightenment, the goal of mahamudra practice.

The most commonly discussed fantasized and impossible manner of existence in Buddhism is literally called "true existence," namely existence truly independent from a relation with mind. Since true existence is, paradoxically, false existence, referring to a manner of existence that is impossible and not at all real, we can perhaps avoid the confusion by using, instead, variations of the term "solid existence."

We can begin to appreciate the complex relation between mind and reality by examining it from various points of view. For example, if we approach the topic in a practical, down-to-earth manner and call the actual way in which we and the universe exist "reality," we live "in reality." On the basis of our everyday experience of reality, we can know and perhaps understand it. This process can only occur through the medium of mind.

If directly experiencing and knowing reality is not sufficient to be able to understand it clearly and we also need to think about it, we can only do so through a conceptual scheme, which is a construct of mind. Furthermore, if we need to formulate and express to ourselves or others what reality is, we can only do so through words or symbols, which are also a construct of mind. Reality exists, but it is a fantasy to imagine that we can experience, understand, prove or describe it independently from the relationship between reality and mind. If we may borrow a term from post-modernist philosophy, we must "deconstruct" reality from being some solid thing "out there."

If we ask how do phenomena exist, we have already involved mind in merely asking the question. Moreover, we can only answer this question by also involving mind. Suppose we reply, Yes, that is obvious, but on a theoretical level don't things exist separately from mind? We would have to say that a theoretical level does not exist by itself, independently from a mind that is either formulating or at least thinking about it. We cannot say anything further about how a theoretical level exists, because to say anything involves language, which is a construct of mind.

In fact, as soon as we raise the issue of how things exist, we have entered the realm of description which can only be carried out by mind. But that does not mean that everything exists only in the mind and that the earth did not exist before there was life on it. An object need not be experienced by a specific mind at this moment in order to exist. But if we are going to talk about how things exist, or try to understand, prove and know it, we can only do so in relation to mind. Mahamudra starts on this premise.

We can formulate the relationship between mind and how things exist in several ways. There are two major approaches in mahamudra. Let us characterize them in very general terms. The first presents what exists in terms of phenomena being either mind or objects of mind – in other words, experience or the contents of experience. Phenomena, including minds, exist merely by virtue of the fact that mind can simply give rise to an appearance or occurrence of them as an object of cognition. We can establish that our children and love for them exist simply because we can know and experience them. The other major approach discusses what exists in terms of mental labeling, which means things exist as what they are simply in relation to words and what words refer to or signify. Phenomena exist as what they are by virtue of being simply the meaning of the words, mental labels or conceptual formulations of them. We can establish that our children and love exist simply because we can give them names that refer to them.

In neither case is the existence of phenomena established from their own side by virtue, for example, of an inherent, findable self-nature rendering them truly what they are, independently from any relation with mind. Our children do not exist as our children because they have some defining characteristic somewhere inside them making them inherently "our children" even if we ourselves never existed. And love does not exist by itself somewhere in the sky with a defining internal force empowering its existence. These are impossible, fantasized manners of existing, and all phenomena are devoid of existing in those ways. The absence of any phenomenon's existing in impossible manners is called its voidness, or "emptiness."

Each of these two approaches entails its own characteristic style of mahamudra meditation on the nature of reality. With the former, we focus on the mind that apprehends voidness as its object and come to realize that all appearances are the play of that mind. With the latter, we focus on voidness as an object of cognition, specifically on the voidness of mind, and come to realize that even mind itself exists merely by virtue of the fact that it can simply be labeled as "mind." With the former, then, we focus on a mind that apprehends a certain object, while with the latter, on an object apprehended by a certain mind.

The Kagyu, Sakya and Gelug traditions of Tibet each transmit lineages of mahamudra presented in its own distinctive manner of explanation and with its own individual style of meditation. All derive from common sources in India transmitted to Tibet during the early eleventh century. Kagyu and some schools of Sakya present mahamudra in terms of the inseparability of appearance and mind. Gelug presents it in terms of mental labeling, while other schools of Sakya combine the two by first seeing the relation between objects of mind and mind itself, and then realizing the nature of mind itself in terms of mental labeling. Kagyu and Gelug present mahamudra methods involving both coarse and the most subtle levels of mind, whereas Sakya approaches this only from the point of view of the subtlest level. Kagyu explains two styles of mahamudra practice – one for those who progress through graded stages and the other for those for whom everything happens at once. Sakya and Gelug describe paths of practice for only the former. The Gelug tradition of mahamudra is known as Gelug-Kagyu because it uses Kagyu-style methods for recognizing the conventional nature of mind and then typically Gelug ones for its deepest nature. In the end, as the Fourth Panchen Lama explains in A Root Text for the Gelug-Kagyu Tradition of Mahamudra, each approach comes to the same intended realization and result. Each leads, on the basis of mind itself, to the elimination of all confusion and the realization of all potentials so that we can each be of fullest benefit to others.