No bag. Not a small bag. Not a personal item. Not a jacket with pockets so deep it qualifies as luggage. Pockets only means your phone, your wallet, your passport if you need one, your keys if you're coming home. Everything fits on your body or it does not come.
This is not for every trip. It is not meant to be. A three-week family trip to Europe requires bags. A long weekend in a city you know well may not. A day flight to a meeting and back does not. The question pockets-only asks is not whether you can always do this — the question is whether you have ever tried, and what you discovered when you did.
The discovery is usually the same. You do not miss what you left behind. The hotel has a toothbrush. The pharmacy has everything else. The restaurant will wash your shirt if you ask. The city has everything the city has, and most of it is better than what you packed. The weight you are not carrying is surprisingly easy to not miss.
What pockets-only requires: a phone with your boarding pass and your hotel confirmation. A card that works internationally. A passport if you are crossing a border. Clothes you are already wearing. That is the complete list. Every object beyond that list is a choice, not a necessity — and choices can be examined.
The Swiss Army knife fits in a pocket. So does the Zippo. The things worth traveling with are small by design, because people who travel figured out a long time ago that small is better. The knife that does not make it through TSA gets left at the hotel or handed to someone who is staying. The trip continues. The pockets are still full of everything that matters.
Phone. Wallet. Passport or ID. Keys if you're returning home. A card that works where you're going. These are the non-negotiables. Everything else is negotiable.
A Swiss Army knife if you're checking a bag anyway or driving. Earbuds. A pen. The things that are small enough to not count as packing.
Everything else is available at the destination. Toiletries. Chargers. A book. The city has a pharmacy, a bookstore, a coffee shop with WiFi. You do not need to bring the city with you.