The Trikaya doctrine (Sanskrit, literally «Three bodies or personalities»; 三身 Chinese: Sānshén, Japanese: sanjin) is an important Buddhist teaching both on the nature of reality, and what a Buddha is. By the 4th century CE the Trikaya Doctrine had assumed the form that we now know. Briefly the doctrine says that a Buddha has three ‘bodies’: the nirmana-kaya or created body which manifests in time and space; the sambhoga-kaya or body of mutual enjoyment which is an archetypal manifestation; and the Dharma-kaya or ‘Reality body’ which ’embodies’ the very principle of enlightenment.
Buddhism has always recognised more than one Buddha. In the Pali Canon twenty-eight previous Buddhas are mentioned, and Gautama Buddha, the historical Buddha, is simply the Buddha who has appeared in our world age. Even before the Buddha’s Parinirvana the term Dharmakaya was current. Dharmakaya literally means Truth body, or Reality body. However all of these Buddha are unified in two ways: firstly they share similar special characteristics. All Buddhas have the 32 major marks, and the 80 minor marks of a superior being. These marks are not necessarily physical, but are talked about as bodily features. They include the ‘ushinisha’ or a bump on the top of the head; hair tightly curled; a white tuft of hair between the eyes, long arms that reach to their knees, long fingers and toes that are webbed; his penis is completely covered by his foreskin; images of an eight-spoked wheel on the soles of their feet etc. Clearly if these were physical marks the Buddha would have been a strange looking individual. But since not everyone was able to discern these marks on him, we can assume that they were either metaphorical, or a psychic phenomenon.
The other thing that all Buddhas have in common, is the Dharma that they teach, which is identical in each case.
In the Pali Canon The Buddha tells Vasettha that the Tathagata (the Buddha) was Dharma-kaya, the ‘Truth-body’ or the ‘Embodiment of Truth’, as well as Dharmabhuta, ‘Truth-become’, that is, ‘One who has become Truth’ (Digha Nikaya). On another occasion, the Buddha told Vakkali:’He who sees the Dhamma (Truth) sees the Tathagata, he who sees the Tathagata sees the Dhamma (Samyutta Nikaya). That is to say, the Buddha is equal to Truth, and all Buddhas are one and the same, being no different from one another in the Dharma-kaya, because Truth is one.’
After the Buddha’s Parinirvana a distinction was made between the Buddhas physical body, rupakaya; and his Dharmakaya aspect. This was an understandable and necessary development. As the Buddha told Vakkali, he was a living example of the ‘Truth’ of the Dharma. Without that form to relate to, the Buddha’s followers could only relate to the Dharmakaya aspect of him. Despite the growth of the stupa cult in which the remains, or relics, of enlightened beings were worshipped, Buddhism sees such things as symbols of the Truth, rather than the Truth itself.
Later Mahayana Buddhists were concerned with the transcendent aspect of the Dharma. So therefore if the Dharma is transcendental, totally beyond space and time, then so is the Dharmakaya. One response to this was the development of the Tathagatagarbha Doctrine. Another was the introduction of the Sambhogakaya which conceptually fits between the rupakaya, now renamed nirmanakaya or created body, and the Dharmakaya.
The Sambhogakaya is that aspect of the Buddha, or the Dharma, that one meets in visions and in deep meditation. It could be considered an interface with the Dharmakaya. What it does, and what the Tathagatagarbha doctrine also does, is bring the transcendental within reach, it makes it immanent.
It has been suggested that there is a parallel here between the Trikaya doctrine and the Three Hypostases of Plotinus. Although the Dharmakaya and the Sambhogakaya certainly do bear some resemblance to The One and the Nous, the Nirmanakaya is hardly comparable to the World Soul, except for the fact that both exist within time rather than beyond it.
Moreover, Plotinus was alive considerably later than the Buddhist dissemination due to Ashoka which itself had a substantial influence on Europe (see History of Buddhism).