Timothy O’Connor presents a novel and powerful version of the cosmological argument from contingency. What distinguishes his argument is that it does not depend on the Principle of Sufficient Reason. This version thus avoids powerful objections facing the Principle. We present and develop the argument, strengthening it in various ways. We fill in big gaps in the argument and answer criticisms. These include the criticisms that O’Connor considers as well as new criticisms. We explain how his replies to a Kantian (...) criticism and to the demand for contrastive explanation fail, and properly answer the criticism and the demand. We develop two new criticisms, the objection from opaqueness and the objection from constitution, and explain how these objections can be answered. (shrink)