In DOB and personal identity: could we have been born couple years off? Part 1 I have asked the readers to conduct a series of thought experiments in which they try to imagine being born couple years earlier/later than their actual DOBs and then ask whether their identities might have remained intact in these alternative histories. I also briefly introduced 5 possible negative answers and one in between. Today it’s time to describe the position where conducting my thought experiment landed me originally, the position that opened up my imagination. This is the position that ‘yeah, absolutely, I could have been born years off, no problem’.
DOB is POB with blurry, but existing temporal limits
To sum this up briefly and generally: it’s is perfectly sensible to assume that we could have been born before or after our actual DOB, while still preserving our identity, retrospectively. Our date of birth in the actual world corresponds to a period of birth (POB), covering a range of possible worlds accessible from the actual world, close enough to include a somewhat arbitrary threshold +/- period. But world histories and cultural circumstances might restrict the implementation of particular life plans. Hence, only a retrospective time window (POB) can be provided within which a particular life decision (and a follow-up plan) can be realised, thereby providing a sufficient (but not necessary) condition of personal identity.
Now switching to the particulars, the examples to help you understand this position.
Let’s assume that I was born on the 17th of December, in 1974, in Budapest, Hungary. These look to me as contingent spatio-temporal facts of the unfolding of the actual world. These might be crucial facts of my life (and totally uninteresting for most other people), but nevertheless contingent. But if something is contingent, it might have been otherwise as well. So I could have been born on the 17th of December, in 1975, in Budapest, from the same two parents, on the same hospital bed, in the 14th district. Or I could have been born in Vienna, Austria, 1973, had my economist father landed that particular job in Vienna couple years earlier. And from a retrospective point of view, evaluating these early life possibilities in 2019, from my current position, living in Cambridge, UK and doing what I’m doing, the life trajectory I had is in accord with these different contingent scenarios of times long past. It is compatible, since being born one year earlier, or later (and let’s drop the spatial aspect from now on, to focus on the more complicated temporal one) would not seem to make a significant difference for the life trajectory that I followed ever since that DOB. All of the big decisions of my life (professional and personal ones) could have stayed the same had I been born in 1973 or 1975, instead of 1974. And the same applies to 1972 and 1976. Still, my initial evaluation stays the same for 1971 and 1977. As the temporal disconnect from my actual DOB gets bigger, however, a somewhat strange feeling starts to spread in me: it becomes harder and harder to claim compatibility from a retrospective point of view (dated today, as in 2019) to life trajectory following those newly stipulated DOBs. My personal history gets confounded by world history. Let’s see a cultural example showing scarcity of opportunity in earlier times possibly limiting fulfilment of a particular life plan. My early teen, decisive, scientific commitment to understand the puzzle of biological aging in order to work towards healthy longevity becomes a less stable and more elusive seed to serve as the top priority and ordering principle of my rational life plan, if DOB is pushed back in the past for thought experimentation. Even born in 1974 it was hard for me to do an MS thesis on biological aging as an undergrad, as there was only one such topic announced out of the many available at that time at the local university I attended. This was because the consensus in the life sciences in the 90s was that aging cannot be researched seriously, as there are just too many variables to investigate it and not enough statistical methods, computational requirements and observable data to handle too many variables included in this broad spectrum phenomena. The tools were just not there. And it was just as unrealistic to do a biogerontology PhD in the late 90s. So had I been born 6 years earlier, I would have had much less chance to realise that life plan. On the other hand had I been born much later, say in 1984, some other top priority might have trumped this initial commitment, not letting to turn it into a full blown life plan and trajectory. This is a curious case, but it might potentially reflect temporal asymmetry: I’m saying that since evaluating this thought experiment about our potential DOBs can only be done in a retrospective manner, our personal identity becomes more (too) fluid, more (too) flexible, too (more) open, so it is not possible to exclude the opportunity that something else happens that might become such a formative experience, coupled with a constitutive decision, as to change my life trajectory, yet preserving my identity. Also it might be that, on the contrary, not that something else important happens that changes everything, but that one could have happened does not happen at all, that not enough time is left to have a formative experience leading to a constitutive, self-defining decision. To rephrase, when we come closer to our present with a potential new DOB, the time period left to realise a trajectory shrinks too much to give it a definite shape.
There’s another point, that applies to both earlier and later DOBs, so preserves temporal symmetry but blurry away personal identity. If social circumstances change too much, if there’s a generational change, these can be constitutive too concerning identity in a sense that they limit the applicable period of birth during which the same formative experience might have occurred.
Let me introduce briefly two more examples that might be limiting the scope of the presented positive and constructive view.
One example relates to people born just before or after or during (in the shadow of) historical cataclysms . These large-scale events can be so formative in the narrative construction of personal identities that sometimes they take over. By this I mean they function not just as necessary conditions of identity but sufficient in a sense that they might trigger decisions to launch identity defining projects. Think for example people born during Second World War and turning into historians trying to understand this lowest point of human history. Here world history might take the main stage of personal histories and form identity knots that cannot be unfolded. So ‘being born a couple years off’ for these people might be too much of a strain on their identities yielding a negative answer.
Another example, is the role randomness plays in the implementation of life callings . Imagine a go player, who decides the sole purpose of their (singular they) life is to become a go master. But to execute their plan they need a strong reinforcement in the forms of winning go tournaments. So for instance , born in 1979, wins a big youth tournament in 1996 but then looses a much bigger one in 1997 and in spite of subsequent attempts ranging over a decade, eventually quits their dream. But had X been born 2 years later, X could have won the 1999 big go tournament (analogy of the 1997 one) in this alternative history as all the other players were in a worse shape than X was at that time. So this would have kept X on the committed trajectory providing an overwhelming impetus to stick to THE plan. Such is the curse of immensely competitive professions.
Finishing this post with a serious (quasi-empirical) objection against the presented view: How can people without early commitments and without an identity-defining project can conduct this years_off thought experiment? Can they conduct it all? Is there an age limit for conducting such thought experiment as middle-aged and older people have a much higher probability to have already built themselves a constructive identity? Or maybe, we can safely assume that formative experiences do happen with everybody during their formative (teens, early twenties?) years so conducting such a thought experiment is valid and feasible for all adults and maybe even for very mature kids launching a stellar career early? Could Mozart have conducted this thought experiment in a sensible way at the age of 9? After all he has composed his first symphony at 8 years old.
 I’m indebted to Ágnes Erdélyi for this example.
 I owe the comment and example to my good friend, Csaba Mérő.