I don't remember this passage in Harman's Prince of Networks, but its a nice one from Latour's Laboratory Life:
Specific to this laboratory is the particular configurations of apparatus that we have called inscription devices. The central importance of this material arrangement is that none of the phenomena "about which" participants talk could exist without it. Without a bioassay, for example, a substance could not be said to exist. The bioassay is not merely a means of obtaining some independently given entity; the bioassay constitutes the construction of the substance. [...] It is not simply that phenomena depend on certain material instrumentation; rather, the phenomena are thoroughly constituted by the material setting of the laboratory. (64)
In the article I'm working on, I connect Latour's interest in assemblage/emergence to Levinas's ethical metaphysic. Ethical in the sense that the ethical relation instantiates existence, such that belonging, precedes being. There is no self without relation to the Other/other/others for Levinas. Similarly, as Harman stresses in his explication of Latour, objects exist in for Latour only as far as we can trace their alliances. Metaphysically, I believe the resonances to McComiskey's Gorgias are quite strong.
With a bit of luck, I'll have this monstrous article submitted by the end of the week.