This is going to be a tad tedious. Over the years I have been taught several different meanings of the Buddhist term translated into Chinese as 空. Note that the Japanese Buddhist go-on reading of that kanji is Ku. I am, at present, convinced that all of the various translations are correct in certain contexts. This is because, it appears to me, that at least three somewhat similar, but different, Buddhist concepts are expressed by ku 空. Possible confusion arises when these different usages are conflated. I think the various uses can be distinguished by looking at their antonyms.
To begin, it appears that most uses of Ku 空 in Buddhist Concepts are figurative. The word literally means sky. It can mean, by inference, empty, void, vacuum, vacant, and so on. The current trendy translation for all uses appears to be emptiness. So, let us first look at where this comes from. When it appears alone, Ku 空 usually seems to be a direct translation of the Sanskrit word Sunyata. This consists of the adjective sunya plus the suffix ta. Sunya literally means zero or nil; but is taken to mean empty in this context. The ta has the same function as the suffix -ness, it makes the adjective into a noun. So sunyata means Emptiness.
As a Mahayana Buddhist concept; sunyata was, I think, developed by Nagarjuna. In its fullness, the concept of emptiness in Mahayana probably covers three areas. First, all phenomena are fleeting, transient, or temporary; therefore they are empty of a fixed identity or self nature. Next, all objects are products of mutually inter-dependent co-arising, therefore they are empty of a separate or independent identity. Finally, it is our mental conception which defines separate objects, and concepts are empty in that they are abstract or noumena, or lacking in any real attributes; except as imputed by the conceptual mind.
The Mahayana concept is derived from a nearly identical concept found in the Nikayas; that of the pali word sunnatta. However, there is maybe a slight difference in literal meaning. We start with sunna; which is the adjective as sunya, it means empty. This is thought to be combined with atta, meaning self. So, this becomes empty of identity, a descriptor of phenomena; derived from anatta {no self, or selfless}. Whereas anatta describes the Five Skandhas {form, sensory perception, mental conception, mental conditioning, and discriminative consciousness}; suna-atta refers to dharmas or conditioned phenomena. I think. I also suspect both were intended as adjectives, not nouns. Anatta = selfless; while sunnatta = unidentifiable?
It is also noteworthy that the Buddha appears to have used formless, arupa or mushiki 無色 as a figurative synonym of sunnatta. At any rate, in all of these cases, rupa or shiki 色, meaning form, is an antonym of Emptiness / shiki 空 / sunnatta / sunyata. Moreover, in the Hridaya or Heart Sutra, the opposite of emptiness appears to be form. The Sanskrit word for form is rupa. If I am correct, it refers to the perception of measurable sensory qualities, chiefly shape, size, & color, that define an object. It is translated into Chinese as 色. go on reading shiki; which literally means color. It also means the other characteristics of sensory perception {vedana} that define an object or phenomenon {'little d' dharma}. However, rupa is not a literal opposite or antomym of sunyata, emptiness is form, and form is emptiness.
In this sense, Emptiness is sort of similar to the concept of non-duality, advata or 不二 funi. However, we are not talking about the same sort of non-duality as in Monism; such as Idealism & Materialism. It is nini 二二 funi 不二. dual, but non-dual; all is sort of one in spirit or noumena, but distinct in 'little d' dharmas or phenomena. I think. Alas, we are not done here, because, in some cases, the opposite of Ku 空 is no longer form, rupa, or shiki 色. Instead, it is ke 假; which means temporary, interim, assumed, borrowed, provisional, makeshift, tentative, conventional. In this usage, ku sometimes shows up as kutai 空諦; in contrast with ketai 假諦. I puzzled over this for years. even decades. Recently, I came up with a tentative answer. That shall be Part Two.
To begin, it appears that most uses of Ku 空 in Buddhist Concepts are figurative. The word literally means sky. It can mean, by inference, empty, void, vacuum, vacant, and so on. The current trendy translation for all uses appears to be emptiness. So, let us first look at where this comes from. When it appears alone, Ku 空 usually seems to be a direct translation of the Sanskrit word Sunyata. This consists of the adjective sunya plus the suffix ta. Sunya literally means zero or nil; but is taken to mean empty in this context. The ta has the same function as the suffix -ness, it makes the adjective into a noun. So sunyata means Emptiness.
As a Mahayana Buddhist concept; sunyata was, I think, developed by Nagarjuna. In its fullness, the concept of emptiness in Mahayana probably covers three areas. First, all phenomena are fleeting, transient, or temporary; therefore they are empty of a fixed identity or self nature. Next, all objects are products of mutually inter-dependent co-arising, therefore they are empty of a separate or independent identity. Finally, it is our mental conception which defines separate objects, and concepts are empty in that they are abstract or noumena, or lacking in any real attributes; except as imputed by the conceptual mind.
The Mahayana concept is derived from a nearly identical concept found in the Nikayas; that of the pali word sunnatta. However, there is maybe a slight difference in literal meaning. We start with sunna; which is the adjective as sunya, it means empty. This is thought to be combined with atta, meaning self. So, this becomes empty of identity, a descriptor of phenomena; derived from anatta {no self, or selfless}. Whereas anatta describes the Five Skandhas {form, sensory perception, mental conception, mental conditioning, and discriminative consciousness}; suna-atta refers to dharmas or conditioned phenomena. I think. I also suspect both were intended as adjectives, not nouns. Anatta = selfless; while sunnatta = unidentifiable?
It is also noteworthy that the Buddha appears to have used formless, arupa or mushiki 無色 as a figurative synonym of sunnatta. At any rate, in all of these cases, rupa or shiki 色, meaning form, is an antonym of Emptiness / shiki 空 / sunnatta / sunyata. Moreover, in the Hridaya or Heart Sutra, the opposite of emptiness appears to be form. The Sanskrit word for form is rupa. If I am correct, it refers to the perception of measurable sensory qualities, chiefly shape, size, & color, that define an object. It is translated into Chinese as 色. go on reading shiki; which literally means color. It also means the other characteristics of sensory perception {vedana} that define an object or phenomenon {'little d' dharma}. However, rupa is not a literal opposite or antomym of sunyata, emptiness is form, and form is emptiness.
In this sense, Emptiness is sort of similar to the concept of non-duality, advata or 不二 funi. However, we are not talking about the same sort of non-duality as in Monism; such as Idealism & Materialism. It is nini 二二 funi 不二. dual, but non-dual; all is sort of one in spirit or noumena, but distinct in 'little d' dharmas or phenomena. I think. Alas, we are not done here, because, in some cases, the opposite of Ku 空 is no longer form, rupa, or shiki 色. Instead, it is ke 假; which means temporary, interim, assumed, borrowed, provisional, makeshift, tentative, conventional. In this usage, ku sometimes shows up as kutai 空諦; in contrast with ketai 假諦. I puzzled over this for years. even decades. Recently, I came up with a tentative answer. That shall be Part Two.
