Just to be contrarian, let me perhaps disagree with what my colleagues have said. It seems likely that the term "beautiful" is what philosophers call "context-sensitive". That is, what it means varies from case to case. The simplest examples of such words are "I", "you", "here", and the like, but most of us have come to the conclusion in recent years that most expressions of natural language exhibit some degree of context-sensitivity. For example, quantifier words, like "all", seem to do so. The sentence "Everyone is on the bus" certainly need not mean that absolutely everyone is on the one and only bus in the universe. What it means clearly varies from case to case. The same seems to go with "beautiful", and in two respects. One is that "beautiful" is a scalar adjective, like "tall", in that it accepts modifiers like "very". And, like "tall", how beautiful something has to be to count as beautiful tout court will vary from case to case. That might make it possible truly to say "Everyone is...

My understanding is that Kant argued in something like this fashion. Or, at least, that Kant thought that it was through the contemplation of beauty that we could experience the divine. I don't myself see that any sort of real argument will be forthcoming along these lines, but I do understand the sentiment. Certainly there is music that makes me particularly conscious of God: Plenty of Coltrane, for example. But for myself, I think my deepest sense of the divine emerges from contemplation of the men and women who have made great contributions towards the emergence of justice in the world. To me, that is, the best argument for the existence of God is the existence of people like Dr Martin Luther King, Jr. I don't expect that to be convincing to anyone else, though.

I don't know that the beauty of a thing is diminished by its prevalence. Roses, blue jays, and the newfallen snow, for example, continue to strike me as stunningly beautiful no matter how often I am privileged to see them. Perhaps there is something different about human creations. Or perhaps, with art and architecture, we respond to something other than beauty, such as originality.

I have no idea. Perhaps a phonologist could answer this question. But let me ask a different one. Do you also find that it is the case that some "nonsense words" sound pretty and some sound ugly? Or is it also important what the word means?