A young Greek named Theseus owns a ship, and he takes good care of it: replacing old planks as they decay, putting in new, stronger timber planks in their places. One day he realizes: not a single plank from the original ship remains – everything has been replaced. Is this still Theseus’s ship? This famous thought experiment has no right answer. It depends on your perspective. Legally, culturally, and metaphorically, the ships definition is continuous: what makes it a ship is not any one part but the concept as a whole. Yet every part has been replaced, so it is no longer the same ship Theseus started with. If each part removed was instead of being thrown away, used to rebuild the ship elsewhere, it’s the rebuilt ship that would most resemble the original.
Your might be surprised to learn your body works the same way as Theseus’ ship. Not a single cell that is in your body today was there when you were a child. Every bit of you has been replaced many times over. But “you” were there... how else could you remember your childhood? The truth is that nothing is permanent: what we call “you”, is simply atoms flowing from place to place, temporarily coming together to form your shape. You only exist as a concept in your own memory, and the memories of others that know you. If everyone’s memories were wiped clean, there would be no more you to speak of. You’d evolve new memes, built on the back of new experiences, without the confines of your prior beliefs.
You propagate through time through your memes: bundles of memories constitute your personality, culture, values, and every time one of those memes is forgotten, some part of you disappears. Over time you evolve, as new memes become associated with you, and old memes are discarded to make you better suited the environment you operate in. This works in much the same way the physical you evolves, through the genes found in your DNA. Except your memes are likely to outlive your genes. Socrates’ genes came to no noticeable consequence, but the memes he passed down are debated in every philosophy class in every university in the world. Since ideas can now be transmitted globally via the internet and recorded indefinitely on computer hard drives, most of the best memes we create may never be forgotten.
You’re like a ripple in the water of a river, but with a different combination of elements and mechanism for persisting. “No man ever steps in the same river twice, for it's not the same river and he's not the same man.” - Heraclitus. Ripples propagate through the water by means of wave motion. A sound propagates through the air in the form of compression and rarefaction. Genes propagate through biological reproduction. Memes propagate from brain to brain through imitation. Everything around you is there because it found a way to persist over time, some more successful than others. As Grand says in Creation, “Things that persist, persist. Things that don’t, don’t.”