In this paper, I analyzed the discussion on the principle of universalizability which took place in moral philosophy in 1970–1980s. In short, I see two main problems that attracted more attention than others. The first problem is an opposition of universalizability and generalization. M.G. Singer argued for generalization argument, and R.M. Hare defended universalizability thesis. Hare tried to refute Singer’s position, using methods of ordinary language philosophy, and claimed that in ethics generalization is useless and misleading. I have examined Singer’s (...) defense and concluded that he was right and Hare was mistaken. Consequently, generalization argument is better in clarification of the relationship between universality and morality than Hare’s doctrine of universalizability, and hence the universality of moral principles is not incompatible with the existence of exclusions. The second problem is the substantiation of the application of categorical imperative in the theory of relevant act descriptions and accurate understanding of the difference between maxims and non-maxims. In Generalization in Ethics, Singer drew attention to this theme and philosophers have proposed some suggestions to solve this problem. I describe ideas of H.J. Paton, H. Potter, O. O’Neill and M. Timmons. Paton coined the teleological-law theory. According to Potter, the best criterion for the relevant act descriptions is causal one. O’N eill suggested the inconsistency-of-intention theory. Timmons defended the causal-law theory. My claim is that the teleological-law theory and the causal-law theory fail to solve the relevant act descriptions problem and the causal criterion and the inconsistency-of-intention theory have their limits. From this, I conclude that these approaches cannot be the basis for clarifying the connection between universality and morality, in contrast to Singer’s approach, which, therefore, is better than others to clarify the nature of universality in morality. (shrink)