Knowledge, as I use this term, is the information that humanity has recorded in a medium and improved over time. There are two crucial parts to this definition. The first is “recorded in a medium,” which allows information to be shared across time and space. The second is “improved over time,” which separates knowledge from mere information.

A conversation that I had years ago but didn’t record cannot be knowledge in my sense—it isn’t accessible to anyone who wasn’t there when it happened, and even my own recollection of it will fade. However, if I write down an insight from that conversation and publish it on my blog, I have potentially contributed to human knowledge. The blog post is available to others across space and time, and some blog posts will turn out to be important contributions to human knowledge. As another example, the DNA in our cells isn’t knowledge by my definition, whereas a recorded genome sequence can be maintained, shared and analyzed. Gene sequences that turn out to be medically significant, such as the BRCA mutation that increases the risk of breast cancer, become part of human knowledge.

My definition of knowledge is intentionally broad, and includes not just technical and scientific knowledge but art, music and literature. But it excludes anything that is either ephemeral or not subject to improvement. Modern computers, for example, produce tons of recorded information that are not subsequently analyzed or integrated into any process of progressive bettering. The reasons for this definition of knowledge will become clear as I use the term in the following sections and throughout the book.

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