Fear conditioning occupies a privileged and contested position in the depth-psychology and affective-neuroscience corpus. At its core, the term designates the Pavlovian process whereby a biologically neutral conditioned stimulus acquires the capacity to elicit defensive responses through repeated pairing with an aversive unconditioned stimulus — a shock, a predator odor, a traumatic encounter. LeDoux’s program, spanning decades of lateral-amygdala research, established the canonical neural circuit: CS and US information converge on pyramidal neurons of the lateral amygdala, where synaptic changes encode threat memory and project downstream to produce freezing, autonomic arousal, and potentiated startle. Kandel’s invertebrate work on Aplysia supplied the molecular vocabulary — long-term potentiation, CREB-dependent transcription — that made cellular accounts of conditioned fear tractable. Yet Barrett mounts a pointed critique: what researchers call ‘fear learning’ is, on close inspection, the conditioning of a freezing behavior, not the conditioning of a phenomenal state called fear; conflating circuit and experience imports a category error into the entire enterprise. Panksepp defends the affective reality of conditioned arousal by showing how cat-odor exposure produces rapid, durable inhibition of play in rats, arguing for a genuine emotional-system activation rather than mere behavioral indexing. Clinical tributaries — PTSD etiology in Shapiro and Lanius, extinction-based exposure therapy in LeDoux, interoceptive conditioning in Paulus — demonstrate why the stakes of the debate extend well beyond the laboratory. The field thus triangulates among mechanistic circuit models, phenomenological objections, and therapeutic translation.