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.