This volume collects Adolf Grünbaum's most discussed essays on scientific rationality. It covers the problem of what it takes for a theory to be called scientific and asks whether it is plausible to draw a clear distinction between science and non-science. It also delves into the debate between determinism and indeterminism both in science and in the humanities, and defends the position of the human determinist. This then leads to a thorough criticism of the current theological approaches to ethics and morality, where Grünbaum defends an explicit secular humanism, as well as to a detailed critique of the prominent theistic interpretations of twentieth century physical cosmologies.