Who are you? A collection of cells that form a mass of muscle, tissue, and bones around 5-7 feet high. A vessel of consciousness existing within the framework of time and space. An amalgamation of memories, character traits, and emotion. You probably have a strong sense of who you are. You are the primary witness of your body, your memories, your thought processes, and your consciousness. Everyone else is just a mere observer.
Somehow, a collection of cells formed you, a sentient being so complex that no one but God himself truly understands. How is it that such simple building blocks can form something so incredibly complex? How is it that we are able to tell that we are alive, that we are who we think we are? Only you can really tell. Everyone else just sees the façade of your internal self. If you disappeared and were replaced with a clone that has your memories, your personality, and your emotions, no one else would be able to know. Only you would know. To your friends and family, the clone is no different than you.
If we were able to make clones of ourselves in the future, what would that entail? Sure, some meat copies of you can carry on your legacy as if you were immortal. But, you wouldn’t be there to witness it once you’re gone. While your clones continue to live your life for eternity, they will not carry you. But, what does it even mean to be you? If someone else can look like you and behave like you, then are they really any different?