&gt; I used to think I could recall conversations, but how do I know they actually happened?<p>That seems trivial to verify; just record details about all conversations you have with everyone. I have been doing this since 2009. I have a 5 MB yaml file with details of every conversations (mostly tags), and I might have an above-average memory but yeah I definitely forget things .... (and sometimes I get some of the details wrong even if a conversation happened just minutes ago).<p>Another way to verify (to yourself only) is to writeup your memory of a conversation, PGP sign it, hash it, give the hash to a friend who was originally in the conversation, then have them do a writeup, then reveal the commitment and compare the two accounts of a conversation. The writeup would be better if it was done immediately after the actual conversation, because otherwise social groups have time to mingle and confuse everyone about what actually happened.<p>Another way is to do a public group writeup of a conversation after it happens (or an audio&#x2F;video recording), then have everyone PGP sign the writeup (to confirm their agreement), then later pick a random conversation where this setup was performed, and write down your memory of the conversation. This doesn&#x27;t work if the conversations where this setup is performed are all unique; probably has to be a few thousand different setups happen before this starts to test memory in any meaningful capacity.