"Most activities that I do require a combination of activity-specific gear and a set of more general core hardware. A ski trip requires specific gear like skies and gloves, but also core hardware like a wallet and a good book. I’ve found that most activities of the same duration and complexity share the same set of core hardware. For example, a 3 day ski adventure, scientific conference, or holiday weekend requires much of the same core hardware.
A byproduct of this division between activity-specific gear and core hardware is that core hardware naturally organizes into layers. Core hardware that I use for shorter duration activities serves as the foundation for core hardware that I carry for longer duration activities. A smaller set of core hardware integrates into the layer above it. Each layer subsumes the previous layer like a series of Matryoshka dolls."
Seth's bag of choice for urban settings? The EB.
"For most urban settings I select the Tom Bihn Empire Builder. The bag has a well thought out design that supposedly took 3 years to develop. The pockets are positioned well the carrying handles are extremely comfortable. I especially like the integration with the Brain Cell for securely carrying a laptop: