Traditions are polarised by Latour into abstract modes and concrete domains.How abstract are the modes? Or, in what way are they abstract? They are produced qua philosophical objects by a process of abstraction, for sure. They are essences abstracted from a more complex and chaotic milieux. But they are not abstract like, say, Whitehead's eternal objects. If Latour is right then the modes are instantiated in every event of their kind. If they cease to be instantiated then they must surely disappear from existence. They have to spread like viruses; to stop spreading is to go extinct. If they are real then they cannot exist in any 'elsewhere' like eternal objects. That sounds an awful lot like concreteness to me.
Consulting my trusty etymology dictionary I find that the root of abstract is the Latin abstractus meaning "drawn away." In this sense the modes are the opposite to 'abstract' - they draw towards, draw together. The modes themselves seem to be, in principle, utterly concrete; the drawing away comes when we divert them from their trajectories to be poked and prodded by our conceptual interrogations. They are concrete beings that, like any being, can be abstracted by reference. We shouldn't mistake their abstracted state for what they are (if we accept that the referential chains are valid).
Anyway, that's enough thinking for one day.