... social does not designate a thing among other things, like a black sheep among other white sheep, but a type of connection between things that are not themselves social.As I've previously argued, for Latour 'social' is not a synonym for 'relation'; it, instead, designates a particular kind of relation. Therefore, to say that something is outside sociality does not mean that it is outside relationality altogether.
... ‘social’ designates a type of link ...
... social, for ANT, is the name of a type of momentary association which is characterized by the way it gathers together into new shapes.
It seems from Reassembling the Social, Paris, Invisible City and, indeed, Latour's own comments in response to Harman's in The Prince and the Wolf that plasma is supposed to be outside sociality specifically rather than relationality altogether. Therefore, the claim that plasma is a metaphysical concept in the sense of something existing beyond all relation is unsupported by what Latour actually says. Indeed, the contrary is rather strongly suggested.
Plasma could be rendered metaphysical (and remain consistent with what Latour says of it) if we understood it to be: (a) that which is outside, enveloping, supporting and feeding any given relational complex, social or otherwise, so long as it was also (b) particular to that network -- in other words, if what was unformatted, unrelated plasma to one complex could be fully formatted and enrolled in another (e.g. that which is plasma with respect to sociality is not plasma with respect to physical existence).
However, to conflate sociality with all relationality and to infer, on that basis, that plasma is outside all relationality requires a fairly large imaginative leap beyond what the text specifies. That doesn't make it any less valid an interpretation (no translation without transformation, the author is dead, etc.) but it does mean, in my opinion, that the gap between the two versions should be acknowledged. Indeed, refusing to acknowledge this gap will only confuse things for everyone.