guided if it occurred, has formalized and revised the improbability argument as the evolutionary argument against naturalism, which asserts that it is irrational to reject a supernatural, intelligent creator because the apparent probability of certain faculties evolving is so low. Specifically, Plantinga claims that evolution cannot account for the rise of reliable reasoning faculties. Plantinga argues that whereas a God would be expected to create beings with reliable reasoning faculties, evolution would be just as likely to lead to unreliable ones, meaning that if evolution is true, it is irrational to trust whatever reasoning one relies on to conclude that it is true. This novel epistemological argument has been criticized similarly to other probabilistic design arguments. It has also been argued that rationality, if conducive to survival, is more likely to be selected for than irrationality, making the natural development of reliable cognitive faculties more likely than unreliable ones. A related argument against evolution is that most mutations are harmful. However, the vast majority of mutations are neutral, and the minority of mutations which are beneficial or harmful are often situational; a mutation that is harmful in one environment may be helpful in another. Unexplained aspects of the natural world In addition to complex structures and systems, among the phenomena that critics variously claim evolution cannot explain are consciousness, hominid intelligence, instincts, emotions, metamorphosis, photosynthesis, homosexuality, music, language, religion, morality, and altruism (see altruism in animals). Most of these, such as hominid intelligence, instinct, emotion, photosynthesis, language, and altruism, have been well-explained by evolution, while others remain mysterious, or only have preliminary explanations. No alternative explanation has been able to adequately explain the biological origin of these phenomena either. Creationists argue against evolution on the grounds that it cannot explain certain non-evolutionary processes, such as abiogenesis, the Big Bang, or the meaning of life. In such instances, evolution is being redefined to refer to the entire history of the universe, and it is argued that if one aspect of the universe is seemingly inexplicable, the entire body of scientific theories must be baseless. At this point, objections leave the arena of evolutionary biology and become general scientific or philosophical disputes. Astronomers Fred Hoyle and Chandra Wickramasinghe have argued in favor of cosmic ancestry, and against abiogenesis and evolution. Impossibility This class of objections is more radical than the above, claiming that a major aspect of evolution is not merely unscientific