Understanding the relationship between genotype and neuronal circuit phenotype necessitates an integrated view of genetics, development, and plasticity/learning. Challenging the prevailing notion that emphasizes learning and plasticity as primary drivers, we delineate a tripartite framework to clarify our view of the respective roles that learning and plasticity might play in circuit assembly. In the first part, called System One, neural circuits are established purely through genetically-driven algorithms, where activity-dependent plasticity serves no instructive role. We propose that these circuits equip the animal with sufficient skill and knowledge to successfully engage the world. Next, System Two is governed by rare but critical "single-shot learning" events, which occur in response to survival situations and prompt rapid synaptic reconfiguration. Such events serve as crucial updates to the organism's existing hardwired knowledge base. Finally, System Three is characterized by a perpetual state of synaptic recalibration, involving continual plasticity for circuit stabilization and fine-tuning. 

By refining the definitions and roles of these three core processes, our framework aims to resolve existing ambiguities and enrich our understanding of neural circuit formation.