It appears then that the following statement of the doctrine represents the correct traditional understanding of syādvāda, in modern terms:
The logical doctrine of Jaina philosophy forms the most important aspect of that school. The fundamental principle of this logical doctrine implies the possibility of a positive and negative predication about the same thing. This doctrine is generally referred to as asti-nāsti, is and is not. According to Jaina logic, affirmative predication about a thing depends upon four conditions - sva-dravya, svakṣetra, svakāla, and svabhāva, i.e. its own substance, its own locality, its own time or duration, and its own nature or modification. Correspondingly, the negative predication about the same thing is conditioned by the four things of an opposite nature - paradravya, parakṣetra, parakāla, and parabhāva, i.e. other substance, other locality, other time, and other nature. This ornament is made of gold, and it is not made of any other metal - are two obvious predications about the same gold ornament, the affirmation (asti) from the point of view of itself (svadravya) and the negation (nāsti) from the point of view of other substance (paradravya). Similarly, it may be said, Socrates was born in Athens, and he was not born in Rome - affirmative predication from svakṣetra and negative predication from parakṣetra point of view, both referring to the same individual. Likewise, we may affirm the historical period of an individual when we refer to his proper time in history (svakāla), and deny his relationship to any other period of time (parakāla). Tennyson lived in the Victorian age and he did not live in the Elizabethan period. In the same way, the last condition, bhāva or mode may be explained. Charles I died on the scaffold, and he did not die in his bed...
...Based upon this principle is the doctrine of saptabhaṅgī, the seven modes of predication. In order to speak of some-thing in relation to its own substance or locality, time or mode, negation or nāsti is to be used. If both the aspects are to be spoken of, then both asti and nāsti are to be used, but one after another. Again, if both the aspects, affirmative and negative, in the same predication, are to be expressed, it becomes inexpressible by language - it is avaktavya. These are the four initial modes of predication in the group of saptabhaṅgī. By attaching the fourth term 'avaktavya' to each of the first three, we arrive at the seven modes of predication: asti, nāsti, asti-nāsti, avaktavya, asti-avaktavya, nāsti-avaktavya, and asti-nāsti-avaktavya. These are the only seven possible modes of predication that we can have.[1]
Kalidas Bhattacharyya, ed., op. cit., pp. 428-429. For a more austere statement of the doctrine in classical terms see Wolfgang Beurlen, tr., op. cit., ppl64-165: 'The sapta-bhaṅgī says that an object (a ghaṭa, of course) seen from a chosen standpoint (syāt) can be signified (1) as existent, (2) as non-existent and (3) as both existent and non-existent (the former seen under its own aspect and the latter under alien ones). The three corresponding formulae are: syād asty eva, syān nasty eva, syād asti nāsti ca. The two statements of (3), however, can be made by letting the one follow the other, whereas they cannot possibly be made simultaneously. Under this aspect the object (ghaṭa) (4) defies description: syādavaktavya eva. The remaining three sentences are identical with the first three by adding avaktavya. This means to say in sentence (5) that a thing exists but that, apart from this positive quality with reference to another thing. It has a negative quality as well, and that it is impossible to express both qualities simultaneously: Syad asti cāvaktavyaś ca. Sentence (6): syān nāsti cāvaktavyacaś is just the reverse on the basis of non-existence. Sentence (7), finally, ca expresses that an object as in (3) can be taken either as positive or negative, though not simultaneously but only successively: syād asti nāsti cāvaktavyaś ca. The wording rendered follows Vimaladāsa's Sptabhāngitaraṅgiṇi (p.2); except for some slight difference it represents the backbone of the Syādvāda literature'.