Hal Finney wrote: >It's an interesting question as to how far we can comfortably >or meaningfully take counterfactuals. At some level it is >completely mundane to say things like, if I had taken a >different route to work today, I wouldn't have gotten caught >in that traffic jam. We aren't thrown into a maelstrom of >existential confusion as we struggle to understand what it >could mean to have different memories than those we do. How >could I have not gotten into that traffic jam? What would >happen to those memories? Would I still be the same person? >We deal with these kinds of counterfactuals all the time. >They are one of our main tools for understanding the world and >learning which strategies work and which don't. > >Then there are much more extreme counterfactuals. Apple >Computer head Steve Jobs gave a pretty good graduation speech >at Stanford last week, >http://news-service.stanford.edu/news/2005/june15/jobs-061505.html. >He explains that he was adopted, and his life was changed in a >major way by the circumstances. His biological mother, an >unwed grad student, wanted him raised by college graduates, so >he was set to be adopted by a lawyer and his wife. At the >last minute the lawyer decided he wanted a girl, so Jobs ended >up being given to a blue collar couple, neither of whom had >gone to college. They were good parents and treated him well, >sacrificing so he could go to college, but after six months >Jobs dropped out, seeing little value to consuming his >family's entire savings. >He continued to attend classes on the sly, got into computers >and the rest is history. > >But imagine how different his life would have been if the >original plan had gone through and he had been adopted by a >successful lawyer, perhaps raised in an upper class household >with his every wish met. >He would have gone to an Ivy League college and probably done well. >But it would have been a totally different life path. > >Does it make sense for Jobs to say, who would I have been if >that had happened? Or would he have been such a totally >different person that this stretches the idea of a >counterfactual beyond reason? I think his telling the story >demonstrates that he does think this way sometimes. >Yet none of the memories or experiences that he has would have >been present in this other version. At most the two versions >might have shared some personality traits, but even those are >often strongly influenced by upbringing - his tenacity in the >face of adversity, for example, might never have become so >strong in a life where everything came easily. >Probably there are many people in the world who are at least >as similar to Steve Jobs in personality as the person he would >have been if his early life had gone that other way. > >The point is that we can imagine a range of counterfactuals >where the difference is a matter of degree, not kind, from >trivial matters all the way up to situations where we would >have to consider ourselves a different person. There is no >bright line to draw that I can see. > >So yes, if you can imagine what it would have been like to eat >something else for breakfast, then you should be able to >imagine what it would have been like to be born as someone >else. It's the same basic technique, just applied to a greater degree.
Those are counterfactuals regarding personal circumstance, and do not seem particularly controversial, even admitting that it is not straightforward to define a single theory of personal identity that "covers all the bases". There's a continuous, definable identity that follows a physical/causal/genetic/mental chain all the way from when egg and sperm met up to Jobs' graduation. It does not seem problematic to alter contingent aspects of this identity-chain and yet insist that we retain the "same" Jobs. It is a great deal harder to see how to make sense of a counterfactual such as "Who would I be if my mother and father hadn't had sex?", or "who would I be if they'd had sex a day later and a different egg and sperm had met?". I have to disagree with you here, and state that this sort of counterfactual seems to indeed embody a difference of kind, not just degree. We're not talking about "imagining_whats_it_likeness". We are talking about me *being* someone different. Jonathan Colvin
