 CA can be considered a paradigmatic locus for the study of phenomena related to emergence (for an introduction, see the entry on  emergent properties).  One can initially divide the problem of emergence into two separate questions, roughly corresponding to epistemological and ontological issues: How can we recognize emergence? What is the ontological status of the high-level properties and features? As a matter of historical fact, CA have been invoked mainly to address the former, but we will see in  Section 3.4  below that there is work for CA also on the ontological side.