Why Turning on Electricity on Shabbat Is Forbidden: The Halachic Logic Behind the Light Switch

In 1883, two of the world’s first commercial power stations were established — one in London and one in New York. From that moment, Jewish legal authorities faced an unprecedented question:
What is the halachic (Jewish legal) definition of activating electricity?

The answer would carry far-reaching implications, especially regarding the laws of Shabbat. All major halachic authorities of the time agreed that lighting or activating electricity on Shabbat constitutes a Torah-level prohibition.

To understand why, we must explore the Talmudic reasoning that forms the foundation for this ruling — specifically, a fascinating discussion in Sanhedrin 77b.

The Case of the Arrow and the Shield

The Talmud presents a scenario: A person shoots an arrow toward a wall or shield. Another person, moments later, removes that shield — and the arrow continues on its path, striking and killing someone behind it.

The Gemara rules: The person who removed the shield is not considered a murderer, but rather one who merely caused a death indirectly.

The reason for this is because removing an obstacle is not the same as performing the act itself. The person did not propel the arrow — he merely stopped blocking it.

The Electric Switch: Modern Parallel to an Ancient Dilemma

We will now apply this reasoning to electricity. Turning on a light switch can be achieved in two ways:

1. By connecting two wires — one of which carries an active current — thus completing the circuit and producing light.

   • In this case, the action is clearly a direct act of ignition, prohibited by Torah law.

2. By removing an insulator — the wires are already connected, but a small non-conductive material (the “barrier”) prevents the current from flowing.

   • When the switch is flipped, it simply removes that insulating barrier — and “there was light.”

Here arises the halachic question: If the switch merely removes a barrier preventing the current, isn’t this analogous to removing the shield from the arrow — an indirect cause rather than direct action?

Rabbi Chaim Ozer Grodzinski’s Investigation

This question was posed to one of the greatest halachic minds of the early 20th century — Rabbi Chaim Ozer Grodzinski (Responsa Achiezer, vol. 3, 60).

Rabbi Grodzinski rejected the comparison outright. To fully grasp the issue, he personally visited an electrical workshop, seeking to understand the physical mechanisms behind electric flow.

He explained that those comparing electricity to the “arrow and shield” case misunderstood the Gemara. The difference lies in how closely the removed barrier interacts with the active force.

When Removing a Barrier Is Considered Direct Action

Later in the same Talmudic discussion, another case is presented:
A person ties someone up and then opens a dam, allowing the nearby waters — which were pressing directly against the barrier, to rush forward and drown the bound victim.

In this situation, the one who opened the dam is considered a murderer, because the barrier was in direct contact with the water’s pressure. Removing it is effectively the same as unleashing the water itself.

The Yad Ramah explains the distinction:

• In the arrow case, the barrier (shield) was not touching the arrow. The act of removing it was separate from the arrow’s motion.

• In the dam case, the barrier and the force (water) were interacting directly — so removing it constitutes direct action.

To clarify further:

• Case A: You remove a roadblock, and a truck already rolling downhill continues and causes harm — indirect.

• Case B: You remove the block holding a stationary truck in place, and it immediately rolls and kills — direct.

Applying This to Electricity

Electric current constantly “presses” against the insulating material that blocks its flow. When you flip the switch and remove the insulator, you are directly engaging with that live current — much like removing the dam holding back the water.

Therefore, turning on electricity is not like removing the shield from an arrow (indirect causation), but rather like opening a dam (direct activation).

This makes it a Torah-level prohibition — a direct act of ignition, or according to other opinions, construction , as it creates a complete circuit.

The “Builder” of the Circuit

The Chazon Ish (Orach Chaim 50:9) adds another layer: When a person completes an electrical circuit, he is building a functional system.

Thus, aside from the issue of fire or heat generation, one also violates the prohibition of boneh — constructing or assembling a working mechanism.

Activating electricity on Shabbat — even by flipping a simple switch, is not a matter of removing a passive barrier. It is, halachically and physically, a direct creative act: unleashing potential energy into active expression.

Through this Talmudic lens, we understand how ancient principles of causation, intent, and direct action continue to guide Jewish law in addressing the most modern technologies — from the arrow and the dam, to the light switch on your wall.