In my previous post I am basically reporting, but also reconstructing, Zizek’s position.
As I report, Zizek does not reply explicitly to Johnston’s feasibility objection, but on my reconstruction there is an answer to be found in the text. Johnston argues that Zizek’s use of quantum mechanics to explain the emergence of free subjectivity starts at a level that is too far from the phenomenon that it is trying to explain and would require a long series of “bridge” theories before getting to the level of the human subject. It is thus more economical to begin with biology and brain science, which occupy levels just adjacent to the human subject, and which equally premise an ontological incompleteness of nature.
The feasibility objection depends on what I call “the argument from distance”, which itself depends on the stratification of levels of emergence (or of reduction, depending on which direction you take, up or down the levels). This is what has been called the “layer cake” model of explanation and reduction.
Zizek’s idea is that on the layer cake model the quantum level is “distant” from the human level, with many other intervening levels, but that from a formal view they are quite close. This means that for him the layer cake model is not always the best or most useful way to envisage the relation between different ontic domains.
The quantum model, for Zizek, deconstructs the stratification of levels:
here quantum physics enters: what makes it so ‘spooky’ is not its radical heterogeneity with regard to our common sense, but rather its uncanny resemblance to what we consider specifically human – here, effectively, one is tempted to say that quantum physics ‘deconstructs’ the standard binary opposition of nature and culture.
Zizek gives primacy to the quantum model not because it is the most fundamental level following the the descending line of reductions and of efficient causality, but because it is the most “deconstructed” model, and thus formally closer to human subjectivity. The sort of causality that Zizek is emphasising here is a formal causality, where the “highest” (or most distant) abstractions are inscribed in the real itself. In other words, Zizek is arguing for a realist interpretation of quantum concepts.
This formal analogy between quantum physics and subjectivity means that the formal causality is operative not only at the “base” or sub-microscopic level but equally at every succeeding level. Real emergence from one level to another, that cannot be explained by reduction to lower levels, is only possible because of the ontological incompleteness that is best described by quantum mechanics (at the present moment).
Zizek does not fetishise quantum mechanics the way Laruelle does. He remarks that the question of which theory best describes the transition from the paradoxical incomplete “proto-reality” to constituted manifest reality is an empirical question:
Therein resides the strength of decoherence theory: it endeavours to articulate the purely immanent way a quantum process engenders the mechanism of its ‘observation’ (registration). Does it succeed? It is up to the science itself to provide an answer.