If Shabbat begins while you're traveling and you have no eruv food, what happens?
Emergency verbal designation: when you can't physically place food, declaring a known spot as your base is valid. Intent replaces physical action when necessary.
Question 2
A person is on a ship when Shabbat begins. What is their base?
Your location at the moment Shabbat begins fixes your base — even if you're in a moving vessel. The ship's position at that moment is your starting point.
Question 3
Someone falls asleep before Shabbat and wakes up after it's begun. Where is their base?
Your physical location at Shabbat's start is your automatic base. Falling asleep doesn't remove the establishment of a base — it just means it's set by location, not intention.
Question 4
Can mental intent alone establish a Shabbat base?
In emergencies, mental intent can replace physical placement. The Rambam recognizes that intent carries halachic weight when physical action isn't feasible.
Question 5
What is the general principle for determining one's Shabbat base?
Default: your physical location when Shabbat begins. This can be modified by an eruv techumin placed before Shabbat, or by verbal/mental designation in emergencies.