I'm going to begin with a long quotation from contemporary philosopher Slavoj Zizek on zombies. I'll then come back and try to tease out some of the meaning. The context of this passage relates to a shift in the understanding of habit in Western thought from the ancients (represented by Aristotle for Zizek) to modernity (represented by Hegel). There's also a dialectical relationship being explored between freedom and habit.
Perhaps, this Hegelian notion of habit allows us to account for the cinema-figure of zombies who drag themselves slowly around in a catatonic mood, but persisting forever: are they not figures of pure habit, of habit at its most elementary, prior to the rise of intelligence (of language, consciousness, and thinking). This is why a zombie par excellence is always someone whom we knew before, when he was still normally alive – the shock for a character in a zombie-movie is to recognize the former best neighbor in the creeping figure tracking him persistently. (Zombies, these properly un-canny (un-heimlich) figures are therefore to be opposed to aliens who invade the body of a terrestrial: while aliens look and act like humans, but are really foreign to human race, zombies are humans who no longer look and act like humans; while, in the case of an alien, we suddenly become aware that the one closest to us – wife, son, father – is an alien, was colonized by an alien, in the case of a zombie, the shock is that this foreign creep is someone close to us...) What this means is that what Hegel says about habits has to be applied to zombies: at the most elementary level of our human identity, we are all zombies, and our "higher" and "free" human activities can only take place insofar as they are founded on the reliable functioning of our zombie-habits: being-a-zombie is a zero-level of humanity, the inhuman/mechanical core of humanity. The shock of encountering a zombie is not the shock of encountering a foreign entity, but the shock of being confronted by the disavowed foundation of our own human-ness.
There is, of course, a big difference between the zombie-like sluggish automated movements and the subtle plasticity of habits proper, of their refined know-how; however, these habits proper arise only when the level of habits is supplemented by the level of consciousness proper and speech. What the zombie-like "blind" behavior provides is, as it were, the "material base" of the refined plasticity of habits proper: the stuff out of which these habits proper are made.
This notion of the need for habit (or necessity) in order to have freedom interestingly is also discussed in process and integral philosophy (which carried it over from process thought). In each moment the entire process of life is alive within us--physical, chemical, biological, evolutionary--and it runs largely on habit. It's our zombie life. And it is this routinization that allows for creativity. What Whitehead called the creativity (freedom) that is added in each new moment. I had never thought of that as zombic however. The rest of the article goes through this dialectical through a number of different dimensions. For example, language: we have to become habituated to speaking (in sentences, with words, in a certain tongue) and only then can we be creatively expressive.
So as Zizek points out it's not simply that our zombic existence is our level of biological habit and then our minds are our freedom but rather the zombic parts of ourselves create habits that allow for the creation of more habits--in the realm of mind, subjectivity, and language--which allow for more freedom. What I like in that is the way it reveals multiple layers of habituation.