The Interpersonal-Psychological Theory of Attempted and Completed Suicide (IPT-ACS) was published by Professor Thomas Joiner in 2005. We provide a brief summary of key psychological constructs in the theory, namely, thwarted belongingness, perceived burdensomeness, and the acquired ability to enact lethal self-injury, followed by a discussion of the role of suicidal ideation in the theory. The rest of the book is a critique of the theory with emphasis on five issues that have not been addressed in post-2005 discussions of the theory. First, we show that in terms of Professor Joiner’s (2005) own narrative of the theories of suicide he used to support the development of his own theory it appears that the IPT-ACS is not a new theory of suicide. Second, Professor Joiner provided several examples (e.g., low suicide rates among twins, relative to non-twins, increasing suicide rates among immigrants, low suicide rates during national tragedy, etc.) to support the main tenet of his theory (i.e., all three constructs must be present for someone to either attempt or complete suicide). We show that Professor Joiner failed to discuss studies that appear to contradict his conclusions regarding those examples. Third, the IPT-ACS attempts to explain certain deaths resulting from the 9/11 terrorist attacks as suicides, rather than homicides as concluded by the New York medical examiner. We show that Professor Joiner’s explanation is not convincing and that it is an insensitive approach in the context of his theory of suicide. Fourth, two important assumptions in the IPT-ACS are: (1) the above three constructs must be present for an individual to engage in the suicidal act; (2) the theory does not apply in the case of individuals who only engage in suicidal ideation or thoughts in the absence of the acquired ability to enact lethal self-injury. We show that both qualitative and quantitative studies in support of the theory have violated these assumptions, suggesting that such studies have not actually tested the main tenet of the theory. Fifth, Professor Joiner recognized that about 95% of individuals who engage in a suicidal act experience severe mental disorder. Professor Joiner, however, concluded that the three constructs in his theory are the explanation of the suicidal act and not mental disorders. We show that this conclusion is difficult to test experimentally, because if it is true that 95% of suicide cases involve mental disorder, any sample selected to test the theory would most likely include individuals experiencing these disorders, suggesting that a test of the theory in the absence of such disorders is a difficult experimental task to accomplish. In addition, Professor Joiner’s theory asserts that one could have the acquired ability to enact lethal self-injury through the process of “vicarious habituation.” We show that it is impossible to empirically test the role of this process in the theory. We conclude that rather than a theory of suicide, the IPT-ACS is a framework that could serve to unify the exemplars of existing theories of suicide.