My understanding is that a concrete conception, as referred to here,
by Marx, refers to conceptions that authentically mirror the concrete,
the material, the phenomena.
All systems comprise of material relations.
I refer to material here because this is directly related to structure.
Concrete is not merely a concentration of abstractions, it is a
concentration that mirrors the phenomena of interest in the concrete
world. Alternatively if we were to implement our concrete conceptions
we would also have a concrete system.
Huw