The case for life on other worlds is examined according to three hypotheses that are presently put forward, viz. 1. That there are numerous planetary abodes for life in the Milky Way and in the extragalactic nebulae. 2. That simple life came into being by a fortuitous assemblage of inorganic matter in the primeval oceans of the earth. 3. That life has evolved from a simple beginning on earth and that it will have proceeded in a similar fashion on the other hypothetical planets. Evidence on each of these three counts is shown to be unsatisfactory and the intellectual edifice one that t is open to considerable doubt. The question of life on other worlds is seen to be an open one.