On the pasuk "Tamim tihye im Hashem Elokecha" (Devarim 18:13), Rashi says :
Conduct yourself with Him with simplicity and depend on Him, and do not inquire of the future; rather, accept whatever happens to you with [unadulterated] simplicity and then, you will be with Him and to His portion
What is the sentiment that Rashi is trying to convey here? Is it that tamim tihye means we should act with simplicity - i.e. we should have simple faith in Hashem and not try to guess the future, but rather simply accept whatever happens as part of His plan?
But if so, then we also shouldn't be looking into the future at all - including using science (which is all about calculating future events) or natural law. But that's just hishtadlus and we do it all the time, and in fact, are obligated to perform.
I understand that maybe this is talking only inquiring of the future from astrologers/diviners. But, again, if the thrust of tamim tihye is the generic notion of simple acceptance of whatever comes, and of not trying to be clever and calculating, then it should have a much broader scope than just astrology.