Our Mishna on amud aleph discusses when encountering an exchange of one coinage for another, what is considered the coin and what is considered the object? This has an effect on the halacha, as in Jewish commerce, payment of money alone cannot acquire a physical object without the object being acquired through some other means such as picking it up. Yet, an object that is not currency can be acquired via exchange or barter. Thus, when one purchases gold coins by paying with silver coins, the gold coins assume the status of the purchased item and the silver coins assume the status of money. (This is because commonly silver is currency.) Therefore, when one party takes possession of the gold coins, the other party acquires the silver coins. But when one party takes possession of the silver coins, the other party does not acquire the gold coins.

Despite the wording of the Mishna, there is a curious discussion recorded between Rabbi Yehuda HaNasi and Rabbi Shimon, his son.  Apparently, when Rabbi Yehuda HaNasi was younger, he taught Rabbi Shimon precisely the opposite: “When one party takes possession of the silver coins, the other party acquires the gold coins.”  How did Rabbi Yehuda HaNasi explain the discrepancy?  He answered, in his youth he held: Gold coins, which are more valuable, are currency; while silver coins, which are relatively not valuable, are a commodity, at least in relation to the gold, i.e., the purchase item or object. The principle is: When one party takes possession of a commodity the other party acquires the currency, but not the reverse. Yet in his old age, he held: Silver coins, 

which circulate, in the sense that they are universally accepted by merchants, in contrast to gold coins, which merchants are less willing to accept as payment for inexpensive items, are considered the true currency. But gold coins, which do not circulate, are a commodity. 

Continuing on the theme from the last daf and looking at the Gemara allegorically, Beis Yaakov on the Torah (Toldos 14) brilliantly captures a truth about the difference between the idealism and energy of youth versus the perspective and wisdom of age.  The Hebrew word for silver coins is “kesef”, which has the same root as “kisufa” desire. (For example, in the liturgy of Yedid Nefesh, we say, “כִּי זֶה כַּמֶּה נִכְסוֹף נִכְסַפְתִּי. For so much has this yearning been.”)  In his youth, Rabbi Yehuda HaNasi his strong desire to acquire Torah (the Gold) was the dominant force, with the goal being the acquisition of the Torah. “When one party takes possession of the silver coins, the other party acquires the gold coins.”  However, in his old age, as the fires of youth calm down and the need for acquisition and mastery changes, Rabbi Yehuda HaNasi realized that the opposite is true. The goal is not the Torah itself, but the desire for Torah. The state of desire allows for the attachment to Hashem.  He realized that a strong knowledge base of Torah will shape the person to develop an even greater desire and attachment to Hashem. He does not need the Torah to be seen as wise or smart; he does not need to accomplish something technical. He wants to attain the level of desire and connection to Hashem that comes from appreciation of the Torah. In other words, he is not preoccupied with attainment, but rather with being in a state of wanting more connection to Hashem for its own sake.