The scientific term you are referring to is called the "principle of mediocrity" or the "principle of cosmic mediocrity." This principle suggests that given the vastness of the universe and the abundance of opportunities for certain events or conditions to occur, it is likely that those events or conditions will occur at least a few times, even if they are extremely rare. This principle is often applied to the possibility of life existing on other planets, stating that with the sheer number of planets in the universe, it is probable that life exists elsewhere, even if it is rare or difficult to find.