His system also offers a low barrier to entry. Psychologists have found that one reason we procrastinate is self-doubt and efficacy issues—the upfront costs of a new project often loom large when future outcomes are so uncertain.

And relations are key.

Like synapses between neurons, note links exponentially increase the value of the system.

First, each card had a unique index number, or address, using numbers, letters, and occasional punctuation based on a branching hierarchy.

an idea, no matter how old or new it is, can always be positioned near other cards on the same topic.

At the bottom of each card, Luhmann would jot down the address of cards with related ideas but positioned under other topics. Following these links, Luhmann could jump across his sprawling note collection and make new connections among ideas.

There is no hierarchy in the Zettelkasten, no privileged place, which means it can grow internally without any preconceived scheme. By creating notes as a decentralized network instead of a hierarchical tree, Luhmann anticipated hypertext and URLs.

purists will point out that existing note-taking apps miss functionality such as backlinking or atomicity.

Roam does seem like a perfect fit, especially when it comes to the atomicity principle. In a Roam document, any chunk of text in any note is a database entity, which means that you can link and relate parts of notes to parts of other notes. Roam even offers a graph of your links, allowing you to visualize the connections between ideas.