Two twin foetus, brother and sister (Boy and Girl) discuss whether Mother exists or not, whether there is life after birth or not. Logic versus intuition; good reasoning versus feelings. Finally both are right. A short story written on 1980, published on 1982; included (with some other short stories) in the book "Morphogeny". On 2006 somebody shared through Internet a micro story with the main idea of this story, with some conceptual errors, but it has spread widely in several languages and I considered by fairness to offer the original source which is quite richer, with quite many more interesting details to consider and think about.