"Since it is already understood to be true to any wise person the necessity of perfection of service [of G-d] and the obligation of its purification and cleansing (for without these it is certainly not desired at all, rather it is disgusting and abominable, for G-d searches out every heart and discerns the formation of every thought), what will we answer on the Day of Reckoning if we slackened in this analysis and put aside a matter which is so incumbent upon us, that is the essence of what HaShem our G-d asks of us? Is it imaginable that our minds should exert themselves and toil in investigations in which we were not obligated, in dialectic from which we gain nothing, and laws that do not apply to us, and that which we have a great obligation to our Creator we should abandon to habit and leave to rote?"

-R' Mosheh Hayim Luzato (RaMHaL, M'silath Y'sharim, Introduction)