When any naturalist philosophy of the sort we find in Lucretius and Deleuze tries to account for thought, consciousness and subjectivity, problems begin to arise. While idealist thinkers begin by taking such categories as givens, and then step back to analyse their functioning through one analytical technique or another, naturalist thinkers can start to sound quite out of their depth when they address questions related to consciousness or thinking. Deleuze holds that thought, minds, consciousness, subjectivity and so on are real, yet still argues that they are the outcomes of genetic processes actualising virtual ideas, that is, they are not causes, but effects whose reality and emergence must be explained. The essential question for such naturalisms is then not ‘How is experience given to a subject?’ but rather, ‘How does the subject emerge amidst the given?’ The task of this chapter is to explain how Deleuze's account of the production of a thinking and conscious being (a subject) is a result of a framework he inherits, at least in part, from the response to this problem offered in Lucretius’ atomic naturalism. The chapter will begin at that far end of this tradition with the Lucretian account of the constitution of the sensing and thinking agent within the atomic world. The second half of the chapter will then turn to Deleuze, where we will account for the emergence of thinking and sensing beings out of the problematic plane of the idea. This plane, we will argue, is found in both Lucretius and Deleuze.

As we saw in the last chapter, divergent processes of individuation emerge from ideas or problems taken as immanent and genetic ontological structures. For Lucretius, this is due to the continuous movement of atoms swirling about the void. Eventually, sets of atoms bombard the affective surface that is the human body (Deleuze also talks about this in terms of the excitations of the body in response to various atomic sparks). Through this process, the body is compelled to react in various ways: it perceives, it remembers, it thinks and so on.