http://en.wikipedia.org/wiki/Anthropic_principle the anthropic principle is the idea that the observations of the physical universe must be compatible with the life observed in it. The principle was formulated in response to the fine tuning/argument from design type arguments, which assert that the universe seems to have been created just for us, as all of the natural laws, and all physical constants contained therein, are conducive to life. The anthropic principle basically counters this contention with a well, duh. Of course it's all conducive to life. If it wasn't, we would not be here to make such observations. You cannot observe conditions of a given universe of you do not exist.