Deleuze does not discuss ALIEN in his Cinema books (more on that later). So we must turn to some of his other discussions to find useful materials, in his analyses of films and also of paintings, and in his theoretical apparatus in general. I see no real break between his film work and the rest, but rather a continuity, so we have lots to draw upon.
In particular, for our present concern with ALIEN, Deleuze finds in the Gothic a notion of abstraction over against the organic form. He proposes the concept of « inorganic life », a mutant flux of vitality unbound by its organic containers. Seen from the point of view of the organism this pure life typically inspires recoil and horror. However, Deleuze points out that there are cases where it is welcomed as a liberation. Deeper than the horror lies the joy of concrete abstraction, becoming an inorganic Entity (his favourite example is Randolph Carter in Lovecraft’s dream cycle).
Another concept is, as we have begun to see, that of the « Anomal », an Entity that exists within a system (body, house, spaceship) that is at the same time radically other to the system, « unnatural » within the terms of the system, an « outsider », a « monster ». He cites « Moby Dick or the Thing or Entity of Lovecraft, terror ». The anomal is for example the demon with which the sorceress can make a pact to open up a new becoming. Ripley has much of the sorceress in her, her affinity with the cat, her increasing sensitivity and her ability to anticipate the alien’s behaviour.
If I have recourse to Deleuze it is to help me make explicit my intuitions and to spell out a feeling that there is something « positive » going on in ALIEN. Jesse Willis on the episode of the SFFaudio Podcast devoted to ALIEN remarks that the « alien » of the title could be either a noun or an adjective. I propose that it can also be interpreted as a verb « to alien », « to other », to become.
ALIEN is a film of becoming. Deleuze’s concepts of « inorganic life » and « anomal » help us to think becoming. Underlying organic life and making it possible is a germinal life that exists within the organism but is not bound by it. This anomalous life force, pure libido, can repurpose, replace, transform, or generate new organs. The anomal, as element that does not fully fit in to the system in which it is encountered, cannot be assigned a fixed identity within that system. The alien is such a biological deconstructive element.
ALIEN is a film of abstraction, anomaly, becoming, and bio-deconstruction and as such exacerbates certain elements of the Gothic.
All this sounds very abstract, but we see Ripley taken up in a process of becoming alien in this first film, progressively losing her official identity as warrant officer, member of the crew of the Nostromo and employee of the Company. Reduced to bare life she comes to identify with a pure drive to survive.
The later films literalise Ripley’s evolution into a genetic hybrid of alien and human, but she is already a spiritual hybrid at the end of ALIEN.