Ribis seems like a very hard issur to comprehend especially in light of modern economic theory. A lot of what we know of pricing of financial instruments are dependent on the time value of money. Inflation, interest rates, future contracts, options, etc.. are priced to a large degree on interest rates.. I don't know what an economy without interest would look like. However, one thing is clear, it is a fundemental part of the economy and is not considered as "taking advantage of" or the other terrible things the Torah seems to be telling us about interest.
The Torah Temima's theory is that in fact interest was a different animal when the Torah was given. It was forbidden in a time when society in general was, economically, agrarian. People lived from crop to crop and the agriculture drove the economy as a whole. Money played a much lesser role. If, in between crops, one had extra cash that would be put in a bank today, it would be considered "Midas Sedom" not to lend that money to a friend in need. People were not making money on their money and there was not much opportunity cost to lending those monies out. Therefore, postulates the Torah Temima, baked in to the issur is the "Heter Iska" which is maligned by many. Actually, the Torah Temima says that "Heter Iska" is not a technical trick to get around ribis but rather a basic necessity in a modern economy where the time value of money is much more relevant.
This theory might have been built on the Torah Tmima's father's theory regarding the Mitzvah of Leket and Peah. The Torah Tmima's father, Rabbi Yechiel Michel Epstein in his Aruch Hashulchan Ha'asid in the beginning of Hilchos Peah asks why do we not keep the Mitzvah of Peah in Chutz La'aretz. He shows that there clearly, according to the Gemarah, is a Mitzvah, at least Derabanan of Peah in Chutz La'aretz. The Aruch Hashulcan Ha'asid hypothesizes that the Din Derabanan of Peah was legislated in an agrarian community where communities subsisted on produce and therefore Matnos Aniyim too consisted mainly of produce. However, he says, today where the vast majority of Jews make a living in commerce, the main Mitzvah of Matnos Aniyim is accomplished by giving Tzedaka and therefore the Mitzvah Derabanan of Peah has been annulled due to neglect or never been legislated for these societies. The Torah Tmima seems to be saying a very similar idea albeit in a much greater scale regarding a Mitzvah De'oraysa. The Torah Tmima says that "Heter Iska" is based on the fact that the Pasuk in Vayikrah 25 36 says at the end of the Issur Ribis "Vechai Achecha Imach" that is to tell you that although there is an Issur it should be practiced within the context of allowing for commerce so that we can live in a healthy and vibrant economy.
Maybe the Torah, realizing the issues facing a ribis free economy actually addresses this by stating "LaNachri Tashich" -To a gentile you SHALL lend with interest. Where else in the Torah do we have an issur where the Torah actually suggests doing what is forbidden to a jew, to a gentile? The Torah is advising us to do to a gentile this terrible act that it considers so bad if done to a jew? The answer is that it is not so bad in a vacuum and needed to run healthy economy so in fact we must lend with interest in general, just not to our brethren.
I once heard that the Alshich explains the reason it is considered such a bad deed is because by lending a person doesn't lose anything per se. The loss is an opportunity cost, ie what he could have done with the money during the loan period. Although opportunity cost is a legitimate cost it is nuanced. We believe in God and should have bitachon. Bitachon means that God will provide for all our needs. We must work within the confines of "Teva"- The natural world. However, when one doesnt do a chesed because he is missing an opportunity that is a blatant statement of disregard to God's handling of his affairs. Yes, you must work and produce and use your money to make money. But you are lacking in faith if you start considering opportunity costs versus the benefits of helping another Jew in need. Opportunities are stuff that God provides. Assuming a loan of similar risk the main rational for interest rate is opportunity cost. Essentially, the time value of money is based on missed opportunity rather than any intrinsic value of the money itself as it would be in other items. A person who lends his car or shovel or house to someone could have used that item himself and that constitutes real value and real loss as opposed to someone who lends money and just needs to be compensated for A) the risk, and B) the opportunity cost of the money lent. Obviously the risk factor still exists but that should not be taken into account as there is a Mitzva of Tzedakah if one assumes he won't get his money back. For one who is worried about getting his money back he is entitled not to lend. The only calculation remaining is opportunity cost for that is the true cost of money, and that is antithetical to true emunah and torah values.
(Another chidush in this pshat might be to explain a Gemarah. The Gemarah that says if one has an opportunity to lend to a non jew with interest and at the same time to lend to a jew interest free, one should choose to lend to the jew rather than the non-jew. This is a seemingly hard Gemarah to understand. Why should a person be excluded from making a living and be forced to lend money rather than lend his money to a non-jew with interest? The Torah never forces someone to do Gemilus Chasadim when he has to go out and make a living? Where do we find the Torah forcing a person to give Tzedaka rather than investing his hard earned money to feed his family? The answer might be that again, if one has an opportunity to lend money to a Jew he must not consider the alternative of making money on his money because that would be considered assuming lost opportunity and tantamount to lending to a Jew with interest. So according to the Alshich not only would one not be allowed to lend Bi'ribis but one would also be prohibited from lending to a non-Jew Bi'ribis when a Jew could benefit from that same money a that same time)
The Maharal takes it a step further by explaining that Jews are all one. We are connected on two levels. The Neshama level- We have all a shared spirit above. Kal Yisrael Yesh Lehem Chelek Leolam Haba. Olam haba connects us through our being Yisrael and everybody has his share in the whole. The physical level. The way we are connected on the physical level is similar to the way we are connected on the spiritual level. Through Eretz Yisrael. We all have a share in Eretz Yisrael, that connection is a very deep physical connection. We are all brothers, but more than that. We are all one and our DNA is connected through the earth of Eretz Yisrael our bodies are one too. The reason we are forbidden to lend with interest is because one does not lend with interest to somebody who he is so connected and close with. This is the reason, the MarHarl says that the Parsha of Ribis keeps on mentioning Eretz Kanaan and our redemption for Egypt. It seemingly makes no sense. However, our being redeemed from Egypt and being taken to Eretz Yisrael is the real reason for the Issur of Ribis.
We became one nation when we were taken out of Mitzraim that is why the Pasuk mentions Yitzias Mitzraim regarding Ribis because it is Assur due to the fact that we are all considered one. Furthermore, Eretz Yisrael solidified our oneness in that having one land combined us on a more physical level.
Both according to the Maharal and according to the other pshat (which might be the alshich) we can now understand why someone who lends B'iribis is considered unworthy to be revived by Tchiyas Hameisim. According to the Alshich he is lacking in fundemental Emunah, and, as the Mishna in Chelek discusses "Eilu Sheh'ein Lahem Chelek Le'Olam Habah" the type of person who loses his share in the world to come is one who is lacking in Emunah. One who lends with Ribis is, on a practical level, the ultimate person lacking in Emunah. According to the Maharal Olam Habah is "Eretz" and as the mishna states "
ועמך כולם צדיקים לעולם יירשו ארץ נצר מטעי מעשה ידי להתפאר ואלו שאין להם חלק לעולם הבא האומר אין תחיית המתים מן התורה ואין תורה מן השמים ואפיקורוס
If one excludes himself from Yisrael and acts with other jews as one who is not connected there is no "Chelek" for him in Olam Habah or Tchiyas hameisim"
