On the basis of three empirical assumptions about the rhythm method and the viability of embryos, Bovens concludes that the pro-life position regarding empbryos implies that it is prima facie wrong to use the rhythm method. Pruss objects to Bovens's philosophical presuppositions and Kennedy to his empirical premises. This essay defends two revised versions of Bovens's argument. These arguments revise Bovens's empirical assumptions in response to Kennedy and, in response to Pruss, supplement Bovens's argument with what I call ‘the principle (...) of parental care’. (shrink)