Why is 空【くう】, and not 無【む】, used to define "void", "emptiness" in a buddhist context? What are their nuances?


_Feel free to participate to the[meta-discussion on whether this type of
question (relying on buddhist terms) should be allowed on
JLU](https://japanese.meta.stackexchange.com/questions/348/should-discussions-
of-buddhist-terms-be-off-topic)._

A while back, looking at a reproduction of some famous zen buddhist scrolls in
a nearby Kyoto temple, I was somewhat surprised to see that the quintessential
notion of "void, emptiness" is represented by '空', rather than '無', to which
my eminently non-scholar mind always gave a more spiritual overtone (beyond
its everyday prosaic use).

A typical example would be the common sentence:

> 色即是空【しきそくぜくう】→ "form is emptiness, matter is void"

Can anybody better versed in Japanese and/or buddhist terms explain to me the
nuances in meaning between these two kanji/words _in a religious context_?

Are there other cases where "void, emptiness" would be translated with '無' in
a buddhist context?

**Edit:** to give a famous example of why '無' would seem a good candidate for
the same concept, Yasujiro Ozu's grave in Kamakura [famously bears nothing but
the kanji
'無'](http://ja.wikipedia.org/wiki/%E5%B0%8F%E6%B4%A5%E5%AE%89%E4%BA%8C%E9%83%8E#.E6.98.A0.E7.94.BB.E4.BA.BA.E7.94.9F),
ostensibly standing for the buddhist concept of 'nothingness'.




I have a feeling someone smarter than me will provide an answer with better
references, but I still hope this answer helps.

Not long ago I was out on a walking tour of Aoyama Cemetery and the exact same
question came up. The tour guide, who has studied religion and history offered
this explanation:

無 （usually な・い, but the on-yomi ム is used in this Buddhist context) means a
complete absence of anything, which I think in English we would equate with
void, so it would seem like the right choice.

空 （usually から, but the on-yomi クウ is used in this Buddhist context） means an
emptiness as well, however, and was used to refer to the air from back before
the more modern and scientific concept that the air is not in fact empty but
contains molecules.

The difference between them is that the emptiness referred to by 空 is, as our
guide explained, like the emptiness inside a cup. It is empty, but is
conceptually bounded by the cup so that it is a space that could hold
something, such as a drink.

無い on the other hand means a complete absence, without even any implication of
potential. In other words, no cup.

In the Buddhist use, then, when you see it on the top layer of the five
elements,
([地,水、火、風、空](http://upload.wikimedia.org/wikipedia/commons/7/76/Pagoda.svg),
earth, water, fire, air, void), implies an emptiness that has a potential to
contain something.

Of course, it gets a little tricky because there is no "cup" for the concept
of all of existence. The void being referred to by 空 doesn't imply that
anything particular should occupy that space. There is no automatic equivalent
for the universe to hold like a drink would seem to be the natural thing to
fill a cup. Just that the void is a vessel into which existence can happen.
And from here the philosophical discussion takes over from the linguistic one.

Side note: 風 （usually かぜ, but the on-omi フウ is used in this Buddhist context）,
or wind, in this context actually means "air", as back in the day, the "air"
was only experienced when you could feel the wind. Before I had this
discussion on the tour, I always thought they were simply differentiating wind
from air.




I have a feeling someone smarter than me will provide an answer with better
references, but I still hope this answer helps.

Not long ago I was out on a walking tour of Aoyama Cemetery and the exact same
question came up. The tour guide, who has studied religion and history offered
this explanation:

無 （usually な・い, but the on-yomi ム is used in this Buddhist context) means a
complete absence of anything, which I think in English we would equate with
void, so it would seem like the right choice.

空 （usually から, but the on-yomi クウ is used in this Buddhist context） means an
emptiness as well, however, and was used to refer to the air from back before
the more modern and scientific concept that the air is not in fact empty but
contains molecules.

The difference between them is that the emptiness referred to by 空 is, as our
guide explained, like the emptiness inside a cup. It is empty, but is
conceptually bounded by the cup so that it is a space that could hold
something, such as a drink.

無い on the other hand means a complete absence, without even any implication of
potential. In other words, no cup.

In the Buddhist use, then, when you see it on the top layer of the five
elements,
([地,水、火、風、空](http://upload.wikimedia.org/wikipedia/commons/7/76/Pagoda.svg),
earth, water, fire, air, void), implies an emptiness that has a potential to
contain something.

Of course, it gets a little tricky because there is no "cup" for the concept
of all of existence. The void being referred to by 空 doesn't imply that
anything particular should occupy that space. There is no automatic equivalent
for the universe to hold like a drink would seem to be the natural thing to
fill a cup. Just that the void is a vessel into which existence can happen.
And from here the philosophical discussion takes over from the linguistic one.

Side note: 風 （usually かぜ, but the on-omi フウ is used in this Buddhist context）,
or wind, in this context actually means "air", as back in the day, the "air"
was only experienced when you could feel the wind. Before I had this
discussion on the tour, I always thought they were simply differentiating wind
from air.

