It is perhaps also worth noting that with a paper-based system you are not forced to split your Next actions into separate context lists. You can have them all one one single list (if you prefer), and simply browse through the list when making your selection: "No, too far away from here", "No, too tired for that", "No, no time now", "No, not important enough". By splitting them up on different context lists you can make things a little bit easier for you if you have lots of actions, but you then also face the classical classification problem - defining contexts that are mutually exclusive on paper while not being entirely so in reality. With a well-designed app none of this would need to be a problem - you could apply multiple independent classifications, such as "requires a computer", "requires John", "requires a quiet environment", "requires a calm mind" and so on, and then simply eliminate tasks requiring those factors that are not present.