I’m currently reading Greg Egan’s Axiomatic. It is a collection of short stories. The ideas in them are extraordinary.
I have certain moral, ethical, and political beliefs. However I know that if a sufficiently strong argument was made against any of these beliefs I could change my mind. I also know that if a billion tiny nanomachines were injected into my skull and rearranged the structure of my brain they could also change my mind.
If, like me, you have decided to reject the idea that human beings are “defined” by an immortal soul then you are left with a wholly materialist (or “physicalist,” as materialist has the wrong connotations...) view of what a person is.
The physicalist view is that everything that makes up a human being can be expressed in the ordinary matter of the universe as we understand it at this point. We don’t have to invoke anything metaphysical to explain consciousness, love, art, mind, personality, or free will.
And if this physicalist view is correct then whenever we change our minds the person we were dies and becomes the person we are now. Of course this is nonsensical. Human beings are dynamic: changing with time. Phillip K. Dick spent a lot of time thinking about these topics:
The two basic topics which fascinate me are "What is reality?" and "What constitutes the authentic human being?" Over the twenty-seven years in which I have published novels and stories I have investigated these two interrelated topics over and over again. I consider them important topics. What are we? What is it which surrounds us, that we call the not-me, or the empirical or phenomenal world?
If my most fundamental beliefs; including: “I love my family” and “killing people is wrong” can be altered in this way then what is it about me that can truly be described as me?
The basic atoms I am made of are constantly in flux, and are rarely the same for more than a month or so. The shape of the pattern of these atoms also changes over time. I have a beginning and an end, and I am of finite physical size. I probably have more in common with people my own age than I do with my “self” from ten years ago.
So what gives? What am I? Does this question mean anything and if so, what is the answer? Egan’s book explores all these themes in a fascinating and readable way. Egan isn’t so arrogant as to offer answers, but he is uniquely gifted in posing the questions.