Scholars have been working on the proliferation question since the detonation of first the atomic bombs in 1945. Yet despite over six decades of fears about the rapid spread of nuclear weapons, only ten states now posses the bomb; and of these only Israel, India, Pakistan, and North Korea developed their weapons after the Treaty for the Nonproliferation of Nuclear Weapons opened for signature in 1968. Nevertheless, numerous states have clandestinely pursued nuclear weapons despite their treaty obligations and the robustness of the nonproliferation norm. What factors prompt some leaders to pursue nuclear weapons, while the vast majority of others choose to rely on the nonproliferation regime, external guarantees, or a combination of the two, for security? To answer this question this study compares nuclear decisionmaking in one state that chose to proliferate - Iran - and a state that did not - Turkey - from the mid-1950s, when they first showed interest in nuclear energy, to the present. To maximize the total number of observations, the study analyzes every nuclear decision made during this period in an attempt to identify the subjective variables influencing decision-makers in both countries. It will be further argued that nuclear decision-making is multi-causal, owing to different conceptions of similar external inputs. As such, nuclear decision-making is country specific, requiring in-depth research to determine the dynamics of proliferation in different countries to determine the reasons why individual states choose to proliferate, compared to the majority that have embraced nonproliferation.