Jowett: immutable

Soc. Then let us proceed ; and where would you have us begin, now that we have got a sort of outline of the enquiry ? Are there any names which witness of themselves that they are not given arbitrarily, but have a natural fitness ? The names of heroes and of men in general are apt to be deceptive because they are often called after ancestors with whose names, as we were saying, they may have no business ; or they are the expression of a wish like Eutychides (the son of good fortune), or Sosias (the Saviour), or Theophilus (the beloved of God), and others. But I think that we had better leave these, for there will be more chance of finding correctness in the names of immutable essences ; — there ought to have been more care taken about them when they were named, and perhaps there may have been some more than human power at work occasionally in giving them names. CRATYLUS  

Str. And you would allow that we participate in generation, with the body, and through perception, but we participate with the soul through in true essence ; and essence you would affirm to be always the same and immutable, whereas generation or becoming varies ? SOPHIST

Str. Then by this admission everything is instantly overturned, as well the doctrine of universal motion as of universal rest, and also the doctrine of those who distribute being into immutable and everlasting kinds ; for all these add on a notion of being, some affirming that things "are" truly in motion, and others that they "are" truly at rest. SOPHIST

Now when the Creator had framed the soul according to his will, he formed within her the corporeal universe, and brought the two together, and united them centre to centre. The soul, interfused everywhere from the centre to the circumference of heaven, of which also she is the external envelopment, herself turning in herself, began a divine beginning of never ceasing and rational life enduring throughout all time. The body of heaven is visible, but the soul is invisible, and partakes of reason and harmony, and being made by the best of intellectual and everlasting natures, is the best of things created. And because she is composed of the same and of the other and of the essence, these three, and is divided and united in due proportion, and in her revolutions returns upon herself, the soul, when touching anything which has essence, whether dispersed in parts or undivided, is stirred through all her powers, to declare the sameness or difference of that thing and some other ; and to what individuals are related, and by what affected, and in what way and how and when, both in the world of generation and in the world of immutable being. And when reason, which works with equal truth, whether she be in the circle of the diverse or of the same — in voiceless silence holding her onward course in the sphere of the self-moved — when reason, I say, is hovering around the sensible world and when the circle of the diverse also moving truly imparts the intimations of sense to the whole soul, then arise opinions and beliefs sure and certain. But when reason is concerned with the rational, and the circle of the same moving smoothly declares it, then intelligence and knowledge are necessarily perfected. And if any one affirms that in which these two are found to be other than the soul, he will say the very opposite of the truth. TIMAEUS  

Soc. There was also supposed to be a difference in sciences ; some of them regarding only the transient and perishing, and others the permanent and imperishable and everlasting and immutable ; and when judged by the standard of truth, the latter, as we thought, were truer than the former. PHILEBUS  

But those who see the absolute and eternal and immutable may be said to know, and not to have opinion only ? THE REPUBLIC   BOOK V

For he, Adeimantus, whose mind is fixed upon true being, has surely no time to look down upon the affairs of earth, or to be filled with malice and envy, contending against men ; his eye is ever directed toward things fixed and immutable, which he sees neither injuring nor injured by one another, but all in order moving according to reason ; these he imitates, and to these he will, as far as he can, conform himself. Can a man help imitating that with which he holds reverential converse ? THE REPUBLIC BOOK VI