Nedarim 26 - 32
To See and be Seen
One who takes a vow to forbid himself from benefiting from "all that see the sun" is forbidden to benefit from anyone, including the blind. This ruling of the mishna is explained in the following way:
Had the one taking the vow intended to exclude the blind, he would simply have said that he forbids benefit from "all who see." By adding "the sun" he indicates that his intention is all things that are "seen by the sun," all things upon which the sun directly shines. This excludes fish which are beneath the surface of the water and offspring in their mothers' womb.
Tosefot raises a question: Perhaps he did not limit himself to just "all who see" because he wanted to exclude only fish who can indeed see but do not see the sun. His answer is that adding "the sun" would not have helped to exclude fish because they do indeed see the sun. It is only because we interpret his use of "the sun" as excluding anything upon which the sun does not directly shine that we are able to exclude fish.
Turei Zahav (Shulchan Aruch Yoreh Deah 217:30) notes that the point made by Tosefot about the fish seeing the sun applies as well to the unborn child. As proof of the ability of the human fetus to see the sun he cites the gemara (Mesechta Niddah 30b) which states that the child in its mother's womb sees from one end of the world to the other. Rashash challenges this application on the grounds that the seeing mentioned there is not a physical one. His challenge is borne out by the dimensions of that vision -- "from one end of the world to another" -- which is certainly not within human physical capacity.
Another interesting point made by Tosefot is that even though we interpret the vow as including all things that the sun directly shines upon, he will not be forbidden to benefit from vegetable and mineral life, only humans and animals. This is because we do not completely disregard what he said about seeing the sun, which limits the vow to those things which have the power of sight. The bottom line is that the vow in this form prohibits him from benefiting from those things which have the ability to see and upon which the sun shines, to the exclusion of fish and the unborn.
What Makes the World Go Round
"How great is the mitzvah of milah (circumcision)," says Rebbie, "for if not for milah, heaven and earth would not be sustained."
Rabbi Eliezer pays the exact same tribute to the importance of Torah study.
Both of these sages base their statements on the passage (Yirmiyahu 33:25) in which Hashem declares, "If not for My covenant by day and night I would not sustain the orders of heaven and earth." They disagree, however, as to whether the day and night covenant refers to the sign of the covenant of circumcision made with Avraham, which is inscribed in the flesh of his offspring by day and by night, or whether it refers to the Torah study which Jews are commanded to be involved in by day and by night.
Maharsha presents a challenge to both of these opinions. In Mesechta Avot (1:18) Rabbi Shimon ben Gamliel states that "the world stands on three things -- on justice, on truth and on peace." Why, he asks, is there no mention of milah or Torah study as one of the world sustainers?
His resolution of the problem is to distinguish between the elements necessary for sustaining human society and what is essential for sustaining the universe in its entirety. Without justice mankind cannot survive, because anarchy leads to violence. The same may be said regarding truth and peace, for falsehood and war destroy human society. These are the three elements which preserve human society which Rabbi Shimon calls "the world." The sages in our gemara, on the other hand, refer to the entire physical universe -- what they call "heaven and earth" -- which is sustained only by the merit of an outstanding mitzvah such as milah or Torah study.