The mishnah introduced on today’s daf deals with a melachah (labor forbidden on Shabbat) that is near and dear to my heart: writing.
One who writes two letters on Shabbat, whether he did so with his right hand or his left, whether they were the same letter or two different letters, whether he did so using two different types of ink, in any language, he is liable.
Rabbi Yosei said: They forbade writing two letters because it is a kind of marking, as they would write on the beams of the tabernacle to know which beam was its partner.
Writing just two letters constitutes a violation of Shabbat. Rabbi Yosei explains the reason: the mishkan was regularly deconstructed and then rebuilt as the Israelites journeyed through the desert. They marked adjacent beams with two markings — an ancient version of Ikea assembly instructions — so they could reconstruct the tabernacle correctly each time.
The word used by Rabbi Yosei is not “write” (kotev) but “draw” or “mark” (roshem). We learn from this that any meaningful mark (not specifically letters, even a pair of scratches, as the Gemara clarifies later) can constitute “writing.” Curiously, writing is not forbidden on Shabbat because of anything physical about the act: neither dyeing parchment, nor chipping stone, nor digging into clay. Rather, writing is forbidden because it creates meaning in a visual manner. In other words, the violation has little to do with the physical world and everything to do with the workings of our mental experience. (And it would, more than a thousand years later, have implications for contemporary rabbinic thinking on e-ink and computer screens.)
But there are limits to the rabbinic ability or willingness to limit “mental labor.” And for good reason. Earlier on this same daf, the Gemara seeks to explain Rabbi Shimon ben Gamliel’s statement in an earlier mishnah that one who strikes an empty anvil with a sledgehammer — even though there is no metal being worked — is liable:
Rabba and Rav Yosef both said: He is liable because he trains his hand for his work by striking the anvil.
The sons of a man named Rahava found this answer difficult: If so, one who observed a craft being performed on Shabbat and learned to perform that craft through observation, would he also be liable?!
Striking an empty anvil creates no physical product. For Rabba and Rav Yosef, however, the act is forbidden because it amounts to physical training — a kind of education. The sons of Rahava dismiss this idea, however, because they see it as having consequences that are far too sweeping: if swinging a sledgehammer is forbidden on the grounds that it is a kind of training, so too it should be forbidden to merely watch someone perform their craft! But as the sons of Rahava point out, forbidding people to simply look at certain things is going too far.
Despite the concern that forbidding kinds of “work” that produce no tangible product constitutes a slippery slope, the idea still lingers in the air when we reach the topic of writing and informs the rabbinic thinking on this restriction. But the rabbis take care to set limits. So while writing is forbidden, reading is most certainly permitted.