The Torah has 613 mitzvos and these are compiled of Chukim and Mishpotim. Mishpotim, are mitzvos whose reasoning we understand and Chukim are mitzvos that are incomprehensible to us. It is here where vulnerability comes in to Jews who are not firm in their emuna and are questioned to explain these. Examples include the red heifer and shatnez. A jew’s response to this is that we have to realise that man is limited hence his understanding is limited while G-d is Infinite. This means that by definition we are lacking in being able to understand and therefore any inadequacy lies with us and not G-d. Thus, any lack of understanding is no reason to stop performing mitzvos.