The article examines the issues concerning the differentiated opinions on protection of human embryos or on using them in research. It analyses the arguments used in laws and in debates about human embryo research. The author has validated the argumentations of Damschen and Schönecker, i.e. the arguments of numerical identity and potentiality, and that of cautiousness. The latter is expanded by the author’s own arguments for the need to protect human embryos and zygotes.