The Mishnah in Pirkei Avot (3, 23) states: “Rabbi Elazar ben Azarya says: Without Torah there is not Derech Eretz (we shall define this term below); without Derech Eretz, there is no Torah.” The simple definition of the term “Derech Eretz” is conducting business, hence the term “way of the world,” for business dealings are the indeed the way of all people in the world.
The meaning of this Mishnah is as follows: If one does not study Torah, the way one conducts business with others in order to earn a livelihood will not be in accordance with the Torah, as the Gemara (Baba Kama 30a) states, “If one wishes to be pious, one should fulfill the laws of [the various Talmudic tractates found in the Order of] Damages” which means that a person must conduct business honestly. If one has not studied these laws, how can one fulfill them? The opposite applies as well. If one does not conduct business with others in order to earn a livelihood, one will have no Torah either, for any Torah that is not combined with some sort of occupation, will eventually become void and bring about sin. Additionally, one will forget one’s Torah learning as well. This is the explanation of the Mishnah according to Rabbeinu Ovadia of Bartenura.
Nevertheless, others explain the term “Derech Eretz” as referring to good and positive character traits, ethics, and manners, for if one does not follow the “way of the world” with regards to manners and ethics, one’s Torah cannot be considered complete since people are not at ease with his actions. Similarly, if one does not study Torah, it is generally impossible for one to have genuine manners and positive character traits in any case.
The Midrash states: “Rabbi Shmuel bar Nachmani says: See how great “Derech Eretz” is, for this preceded the Torah twenty-six generations, as the verse states, ‘To guard the way of the Tree of Life’”- “Way” (“Derech”) refers to “Derech Eretz” (manners and good traits) and “Life” refers to Torah. Similarly, the verse in Mishlei states, “If a man has a worry in his heart he should bend it over and a good matter shall gladden it.” The Vilna Gaon explains that “good” refers to Torah, for anyone who accepts upon himself the yoke of Torah will have the burden of worry removed from himself, as it states in Avot of Rabbi Natan, “Anyone who places the words of the Torah on his heart shall have the fears of sword, hunger, and the like nullified from himself.” It is quoted in the name of Hagaon Harav Nachum of Chernobyl that all worries are forbidden besides for worrying about worrying.