A man gets his arm amputated and it is replaced by a prosthesis that operates via brain signals. Can he use his artificial hand to type on Shabbat? Do the neural messages being sent by his brain constitute a physical act or are they just intangible thoughts?
And if someone breaks that arm, is he liable for property damage or does it constitute personal injury?
What if we can operate a car using the same brain signals, without having to touch the gas pedal, turn the steering wheel or step on the brakes? Could observant Jews start driving on Shabbat? Would we be responsible for the damage caused if we had an accident?
Normally, operating a car or typing on a computer is prohibited on Shabbat. Mankind is supposed to stop all creative acts on the day of the week that, according to Jewish tradition, God "rested" after creating the world.
If I just think about doing something, I have not upset my restful state. But if those thoughts have tangible consequences, should they be forbidden on Shabbat?
These were some of many questions raised by a group of halachic scholars and scientists Wednesday at Bar-Ilan University's Nitzotzot ["sparks"] lecture series, held at the Ludwig and Erica Jesselson Institute of Advanced Jewish Studies Beit Midrash.
As technological advances move ahead at a mind-boggling pace, ethicists as well as halachic authorities have been confronted with a slew of new moral and religious dilemmas that need to be addressed.
"Scientists are developing artificial arms and legs that are controlled by neural signals, not by muscles and tendons," said Rabbi Shabtai Rappoport, head of the beit midrash. "These prostheses are able to duplicate many of the functions of a human hand or leg, including many fine motor skills. But they also raise new halachic questions."
The technology is called Brain Computer Interface or BCI, which can be either invasive - a brain chip is place inside the brain - or semi-invasive - a chip located inside the skull but outside the brain's gray matter.
Non-invasive BCIs have been less successful since the skull dampens the signals, dispersing and blurring the electromagnetic waves created by neurons.
When the subject thinks about moving his hand, he produces signals which succeed in moving a prosthesis.
But how does Halacha define such a limb? Are these gadgets kosher?
"The purpose of our meetings is to raise questions - not necessarily answer them," said Rappoport.
"However, one of the factors that might determine whether using prostheses like these for operating a car or writing on a computer screen on Shabbat is social convention. If the use of this technology becomes an accepted form of transportation or writing, it is more likely that we will relate to it as a desecration of Shabbat."
Rappoport said that this was what has happened with Halacha's approach to writing on computers.
"When the first computers began to be marketed, many rabbis ruled that writing on a screen was not considered to be an act prohibited by the Torah," said Rappoport. "That's because it was considered a novel, different way of storing information.
"But I believe today that writing on a computer screen is probably the most common way of storing information. So the approach should change."
Rappoport said that Halacha's perception of BCIs would probably run a similar path.
"At first, perhaps, we might tend to see this technology as an unusual way of performing tasks. But as they become more mainstream, attitudes are bound to change."
Rappoport used the example of the etrog
(citron) to illustrate how social convention dictates halachic definitions.
Observant Jews use the etrog in a religious ceremony during the Succot holiday. However, since the fruit is delicate and cannot be used if it is blemished, it is common for growers to graft a citron branch onto a lemon tree to strengthen it.
According to Jewish law, a citron that grows in this way is disqualified for use in discharging one's religious obligation.
"If we look at this from a scientific point of view an etrog that grows in such a fashion should be completely kosher," said Rappoport. "The fact that the branch was grafted onto a lemon tree does not change the fundamental composition of the etrogs that grow on the branch. It is like planting the branch in soil.
"But since people look at the tree as a lemon tree and see the citron branch as secondary to the tree, the Halacha does also. The same would hold true for an artificial arm or leg if it is perceived as an integral part of a person's body."
Other speakers included Rabbi Dr. Dror Fixler from Bar-Ilan's School of Engineering, who charted the technological developments from past to present. According to Fixler, the serious challenge will present itself when today's preliminary developments that enable thoughts to operate computers become commercially available.
"These developments, which are currently part of the world of computer games or restricted to institutes of academic research, will pose a serious challenge to halachic authorities as regards the boundaries of what is permitted and forbidden on Shabbat," said Fixler.
He was followed by Israel Belfer, a doctoral student who showed the increasing difficulties of drawing the line between what is human and what is a machine.
The moderator was Rabbi Dr. Tsuriel Rashi, head of the Communications Department at Lifshitz College and a lecturer at Bar-Ilan University.
"Ideas that were once considered crazy or science fiction are becoming reality," said Rashi, "and Halacha is providing solutions to the moral and ethical questions raised by this new reality."