TIDE in the Hirsch Chumash: Secular Studies

"If we understand these sentences of the תייכ aright, then the sentence which stands at their head: forewarns one not to take the following sentences to mean that one is completely to ignore and remain in ignorance of all knowledge and science which has been gained and nurtured by non-Jewish sources or which have no direct bearing on the knowledge to be gained by the study of the Torah. Inasmuch as what is commanded is: עשם עיקר ואל תעשם טפלה, the permission to occupy oneself also with other spheres of knowledge is assumed. Only, the knowledge of the Torah and the understanding we derive from it is to be our principle concern and to be regarded as having been given to us as the absolute and firmly established Truth. Only as accessory knowledge and in as far as they serve to truly help the study of the Torah and are subordinated as the טפל to the עיקר, are they to be studied. But the Torah and all its teachings must always remain that which we have received from Above and must be the yardstick by which we measure all the results obtained by other spheres of learning. Only that which is in accordance with the Truths of the Torah can remain true for us. All that we accept intellectually as well as all our actions must always be considered from the point of view of the Torah and be within the lines of the doctrines it teaches, so that we only accept and adopt  that which is in accordance with them, and do not adulterate the knowledge we draw our of the Torah with ideas which have developed form other and strange premises."

R' Hirsch, Chumash, Leviticus, 18:5, trans. Isaac Levy, Judaica Press.