Some people believe that life will arise spontaneously somehow, somewhere, if conditions are right; and that having arisen it will evolve. But such people neglect to take into account death, which results if a single niche dimension becomes zero, i.e. if a single environmental or other condition does not fall within the range in which it must lie for life to be possible. If such a dimension should become zero, that means death for the individual, and extinction for the species. A few niche parameters, especially some which have a bearing on the question, whether life might exist elsewhere than on Earth are discussed.