I’ve been thinking about the description of the ‘measuring art’ at the end of Plato’s Protagoras as the ‘saviour of our life’ or perhaps the ‘preservation of our life’ (356d3: σωτηρία τοῦ βίου). Does anyone know of any specific discussion of this term? [Update: Ah! How could I have forgotten Nussbaum in FOG ch. 4? That's my next port of call.] Anyway, this is as far as I have got on my own.
A quick glance at the use of the term sōtēria in other authors suggests that it is mainly used in cases in tragedy, for example, when a character hopes or despairs for their lot. Here sōtēria is something wished for. It is simple survival. A similar use can be found in Thucydides. A broader meaning of ‘preservation (sc. of one’s current state)’ can be found in other writers such as Aristotle.
Commentators have rightly wondered whether the measuring skill is offered to Protagoras in part because Socrates cheekily alludes to the sophist’s most famous pronouncement that ‘man is the measure’. But Socrates’ use of the term sōtēria here for his proposed art of measurement is another allusion to another originally Protagorean idea, this time taken from earlier in the dialogue itself. As part of his great speech, Protagoras had told a story of how Epimetheus set about arranging a division of powers between the various new species of living creatures. sōtēria occurs there too.
320e3: To some animals he gave claws or horns and to others he gave some other means for their sōtēria.
321b6: Those species who were preyed upon by others he made more numerous for the sōtēria of the species
321c8ff.: As a means of sōtēria for mankind, Prometheus gave them fire and technical skill (entekhnos sophia sun puri).
Here, sōtēria seems also to mean survival or preservation. Some animals have claws in order not to starve; others are numerous so that they do not become extinct through predation. Humans were able to survive despite their lack of physical defences against predation and the elements due to their intellectual abilities.
This is interesting to me because the measuring art at the end of the Protagoras is often compared with a hedonic calculus and imagined to be a means of maximising pleasure over a life. This maximising role does not seem to me to be well captured in the term sōtēria, which would seem rather to suggest that the measuring art is there to prevent us from falling prey to our own ignorant or unthinking appraisal of goods. Socrates is perhaps, in that case, cleverly turning the possibility of akrasia or, rather, the ignorance often mistakenly taken to be akrasia, into a threat to our lives as pressing as the need to avoid hunger, cold, thirst, and the attentions of naturally much better armed creatures.