'Is it true, O Lord!' asked Gautama, 'that the unstable changes while the stable does not change, the unstable breaks whereas the stable does not break?'
'Yes, Gautama! This is exactly so.'[13]
A substance is the co-eixstence of the unwavering and the wavering, the stable and the unstable. It is immutable and mutable both. The soul is immutable and as such it never changes into non-soul. It is also mutable and as such it passes through various forms of existence. This is explained in the following dialogue between Maṇḍitaputra and the Lord.
Maṇḍitaputra: 'Is it true, O Lord! that the soul is constantly subject to wavering and as a result it passes through various states?'
Lord: 'Yes, Maṇḍitaputra! This is true.'[14]
The same has been said to be true of a material atom which has been regarded as an ever-changing entity in Jainism.[15]
The permanence of the substance is due to its unwavering character (the attribute of immutability), while its impermanence is due to its wavering character (origination and cessation). This is manifest from the following dialogue:-
Gautama: 'Is the soul permanent or impermanent, O Lord?'
Lord: 'The soul is permanent in some respect and impermanent in another respect. It is permanent in respect of its substance (which is eternal) and it is impermanent in respect of modes which originate and vanish.'[16]
This is true not only of the soul but of all other substances which are neither absolutely permanent nor absolutely impermanent, but both permanent and impermanent.
Ibid, 1.440
se nūṇam bhante! athire paloṭṭai, no hire paloṭṭai? athire bhajjai, no thire bhajjai? - hantā goyamā! athire paloṭṭai, no thire paloṭṭai. athire bhajjai, no thire bhajjai....
jīva ṇaṁ bhante! sayā samitaṁ eyati, yeyati, calati, phandai, ghaṭṭai, khubbhai, udīrai, taṁ taṁ bhāvaṁ pariṇamai? hantā maṇḍiaputtā! jīve ṇaṁ sayā samitaṁ eyati-taṁ taṁ bhāvaṁ pariṇamai.