Am I the same person that I was 20 years ago?

[Pendaric]

My understanding is that the entire human body regenerates itself over a long enough period, to the extent that none of the physical material that comprises me is the same as it was 20 years ago.

My opinions on several issues have altered. I no longer hold many of the same opinions and beliefs that I did 20 years ago.

So, my question is - how am I actually related to the person going by my name who existed 20 years ago? Does that person still exist in any meaningful sense? If I don't share the same physical components or the same intellectual makeup, am I actually a different person in more than a romantic meaning of the term?

Will I effectively be dead 20 years from now, even if there is some future me which is a continuation/progression of this state of body and mind?

I'm saying me, but obviously it applies to every single human being on the planet. Could this be an effective defence for a criminal caught 25 years after a crime was committed - 'it wasn't me, the person that I am didn't exist 25 years ago'.

Does anybody get what I am trying to say here, or am I talking gibberish?

[Febble]

My understanding is that the entire human body regenerates itself over a long enough period, to the extent that none of the physical material that comprises me is the same as it was 20 years ago.

My opinions on several issues have altered. I no longer hold many of the same opinions and beliefs that I did 20 years ago.

So, my question is - how am I actually related to the person going by my name who existed 20 years ago? Does that person still exist in any meaningful sense? If I don't share the same physical components or the same intellectual makeup, am I actually a different person in more than a romantic meaning of the term?

Will I effectively be dead 20 years from now, even if there is some future me which is a continuation/progression of this state of body and mind?

I'm saying me, but obviously it applies to every single human being on the planet. Could this be an effective defence for a criminal caught 25 years after a crime was committed - 'it wasn't me, the person that I am didn't exist 25 years ago'.

Does anybody get what I am trying to say here, or am I talking gibberish?

I get what you are saying.

[Pendaric]

And what are your thoughts on it?

[Febble]

And what are your thoughts on it?

Probably the same as David B's, and derived from Dennett/Hofstadter.

Yes, I think you are "the same person" in the sense that when you use the word "I" you refer to something that includes your history - your trajectory through space/time and the experiences/decisions collected along the way. And you have privileged access to those.

Whether you need claim "responsibility" for much earlier actions seem to me to depend on where you set your own boundaries of yourself. As Dennett says, the act of accepting moral responsibility is a self-forming act. You are free to exculpate yourself from various things (and to be healthy you probably should) but by doing so, you are reducing the boundaries of yourself.

And, as Dennett says (in Freedom Evolves)

If you make yourself really small, you can externalize virtually everything

IoW - you choose - but remember that the more you externalise, the smaller you become :)

[Febble]

I wonder if David B is the same person now he has a beard?

[Jobar]

I'm not *quite* the same person I was 20 seconds ago. :)

But, what most defines us as a person is continuity of memory, and identity. I'm certainly not the small boy who didn't want to get on the bus after the first day in the first grade back in 1961, although I still have a memory of being that little boy. But, that boy and I are part of the same pattern, the same wave moving through space and time. I still answer to the same name that boy did, and even still have some of the things that boy called his own. (The Bible on my desk, given me by my grandmother at age 6, for instance.)

So, in one sense, I am that little boy; but he would not have been able to say he would become the person I am now.

Even if I for some reason lost all my memory, my body would still possess the same genetic heritage that boy did. However, IMO that would make me less "the same person", the same "I".

[David B]

Like the River Thames 30 years ago, or NY City 30 ago, there's enough to make the river and the city meaningful concepts, but they, like you and I, are not quite the same as they were 30 years ago.

David

[munnki]

Puts a whole new spin on the Democritus saying 'You can't step in the same river twice.' Now the you has emphasis rather than the river. How trippy....

[Eudaimonist]

"Am I the same person that I was 20 years ago?"

That all depends on what you mean by the word "same". You could mean it in a very literal sense in which no comparison will ever reveal sameness (you can't bathe in the same river twice), or you could have some purpose in mind for regarding two entities at different points in time as the "same" entity. Ask yourself, what is your purpose for using a particular concept of sameness?

I personally have no difficultly seeing myself as the "same" person I was when I was a child in one respect, and as a different person in another respect.

The sense in which I am the same is that I can be connected by biological and psychological causality to my past form. My current form was a potential of my past form. For the purpose of speaking of the dynamic lives of individuals, I am the "same" person. This is useful socially and when reflecting on my life.

OTOH, when comparing quantum states, I am not the same person I was back then.



eudaimonia,

Mark

[Danhalen]

The relation between synchronic and diachronic personal identity is difficult to express for a multitude of reasons. Although there has been a huge amount of contemporary discussion on the topic, I don't think the basic problems that Hume confessed to in his Treatise have been solved (or even made more palatable).

As Mark has pointed out, identity (sameness) is the first issue that needs to be dealt with. Given that a material mass is constantly exchanging atoms and subatomic particles, what does it mean when we identify 'material mass x'? The diachronic identity of a particular material mass is qualitative, while the synchronic identity is quantitative. How do we justify the reduction of the qualitative to the quantitative? Perhaps the reduction of one to the other is an inappropriate term, but in any case, there is a conflation of types of identities. It seems to me that identity is not a quality that resides in the object; it is imposed on the object by the subject.

The major problem for me is the nature of the I. Kant's dissection of the cogito was brilliant. Descartes seemingly ignored the fact that "I doubt" assumes "I exist." Kant's insight into Descartes was the co-referential treatment of the "I". And we fall into the vertigo of Cartesian circles. I find Kant's solution a bit disappointing. The transcendental I merely pushes the problem back one more step by adding an epicycle to defend the existence of the I. But, given a transcendental I, the question asked by the OP seems silly--unless we try to determine the nature of the transcendental I. Yet Kant was clever to place it in the realm of the noumenal. He avoids the question of the I's identity by making it unknowable. My approach would rely on the source of identity I pointed to in the prior paragraph: the subject. Philosophically, I deny the existence of the I.

I suppose I take a Wittgensteinian approach to the question. I cannot be certain of the existence of you or me sans context. So the question of whether or not I am the same person I was twenty years ago must be given parameters by which I can be certain of the answer. What would the consequences be if I were the same person I was twenty years ago? The answer to this question would determine the context by which I can be certain. Then I take the context informing question and ask: what would the consequences be if were not the same person I was twenty years ago? Given the consequences to the first question, if the second question makes no sense then I can be certain that I am, in fact, the same person I was twenty years ago, and my skepticism was unfounded.

[Matty]

Yes, I think you are "the same person" in the sense that when you use the word "I" you refer to something that includes your history - your trajectory through space/time and the experiences/decisions collected along the way. And you have privileged access to those. This. Damn well put as usual Febble.

[munnki]

Wasn't Heidegger's definition of being - 'maintaining a state through time' - is this contradicted? What is being maintained and who is maintaining?

Lawdy...

[Jobar]

In another sense, "I" am the total system which produces Jobar; in the words of Alan Watts,
Underneath the superficial self, which pays attention to this and that, there is another self more really us than I. And the more you become aware of the unknown self -- if you become aware of it -- the more you realize that it is inseparably connected with everything else that is. You are a function of this total galaxy, bounded by the Milky Way, and this galaxy is a function of all other galaxies. You are that vast thing that you see far, far off with great telescopes. You look and look, and one day you are going to wake up and say, "Why, that's me!" And in knowing that, you know that you never die. You are the eternal thing that comes and goes that appears -- now as John Jones, now as Mary Smith, now as Betty Brown -- and so it goes, forever and ever and ever.

[Danhalen]

Wasn't Heidegger's definition of being - 'maintaining a state through time' - is this contradicted? What is being maintained and who is maintaining?

Lawdy...Heidegger had different senses of being. Maintaining a state through time doesn't seem to capture what Heidegger was trying to say about being a specific human (Dasein and later Dasyne). The phenomenological study of being human, according to Heidegger, does not focus on what it is to be human, he focused on how humans exist (because we cannot see what "being human" is in itself). Trying to discover what humans are betrays how humans exist; it makes them "present-to-hand" (they are objects that we observe like we observe a hammer). Describing how humans are is the proper way to go about learning what it means to be human; what do humans do? Dasein is the point at which possibility is made actual by becoming; it is existence humaning (to try and use Heideggerian speak). The I, being transcendent, cannot be observed, and so phenomenology does not try to identify it. I think Heidegger would think the question of the OP is misguided. I think Heidegger is wrong.

[munnki]

Wasn't Heidegger's definition of being - 'maintaining a state through time' - is this contradicted? What is being maintained and who is maintaining?

Lawdy...Heidegger had different senses of being. Maintaining a state through time doesn't seem to capture what Heidegger was trying to say about being a specific human (Dasein and later Dasyne). The phenomenological study of being human, according to Heidegger, does not focus on what it is to be human, he focused on how humans exist (because we cannot see what "being human" is in itself). Trying to discover what humans are betrays how humans exist; it makes them "present-to-hand" (they are objects that we observe like we observe a hammer). Describing how humans are is the proper way to go about learning what it means to be human; what do humans do? Dasein is the point at which possibility is made actual by becoming; it is existence humaning (to try and use Heideggerian speak). The I, being transcendent, cannot be observed, and so phenomenology does not try to identify it. I think Heidegger would think the question of the OP is misguided. I think Heidegger is wrong.

I'm glad you've posted on Heidegger - I attempted Sein und Zeit but found it too difficult to concentrate on. I'm afraid I didn't get far enough to know whether Heidegger was right or wrong. The 'maintaining a state...' was a quote a friend made about the text... I'm still not sure if I should try again...

[Danhalen]

I'm glad you've posted on Heidegger - I attempted Sein und Zeit but found it too difficult to concentrate on. I'm afraid I didn't get far enough to know whether Heidegger was right or wrong. The 'maintaining a state...' was a quote a friend made about the text... I'm still not sure if I should try again...The only reason I struggled through Being and Time is because I had to. You could always try Sartre's Being and Nothingness if you want to read a more accessible philosophy inspired by Heidegger. I found it easier to comprehend than anything Heidegger ever wrote.

[Haswell]

Is it not the case that brain cells (neurones) do not regenerate? If this is so, you as a person are the same as you were 20 years ago, despite the regeneration of your other cells.

I ownder how many organ transplants you would have to undergo to be someone else?

Footnote: I could not bear to be a recipient of a lung transplant. Imagine coughing up someone else's sputum the rest of your life?

[Valheru]

People change, it's a reality of life. We have memories that link us with who we are in the past, but even our interpretation of those memories change as we change, without even realising it.

That whole "leopard doesn't change its spots" schtick is a load of horseshit.

[Eudaimonist]

Is it not the case that brain cells (neurones) do not regenerate?

This might not be true, but let's say it is.

If this is so, are you not the same 'person' as you were 20 years ago, despite the regeneration of your other cells?

Why would having the same brain cells make you the same person? Brain cells are not static. They form new connections over time.


eudaimonia,

Mark

[Angra Mainyu]

Is it not the case that brain cells (neurones) do not regenerate?

This might not be true, but let's say it is.


This article (http://www.nytimes.com/2005/08/02/science/02cell.html?_r=6) cites some research that suggests some and perhaps all of the neurons in the cerebral cortex aren't replaced.

[Iblis waswas]

Biology is the science I know the least about, but in a recent conversation with a biologist at uni I was informed that all the cells in the human body have regenerated over a ten year period as opposed to 20.

To the original question, I would say that we are all different people as we grow older. I have almost nothing in common with the person I was 10 years ago. My political stance has completely changed, my views on religion, my beliefs about society etc. I have no idea what I'll be like in another 10 years.

[lpetrich]

I brought up this issue or a similar one in the "Stuffism" thread, in discussing how Ed of IIDB/FRDB had apparently disbelieved in emergent properties.

I think that continuity of identity here is structural, and independent of the specific material.

Different parts of our bodies turn over at different rates. For instance, we have about 4.7 - 5 liters of blood, and we excrete about 1 - 2 liters of urine per day (numbers from Wikipedia). That means that the water in our blood has a turnover time of 2 to 4 days.

For common domestic-animal species, I could find The Merck Veterinary Manual -Blood Transfusions (http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/10303.htm) and Urine Volume and Specific Gravity* (http://www.merckvetmanual.com/mvm/htm/bc/tref4.htm). They have similar turnover times.

Turning to blood cells, human platelets last about 9 days, red blood cells about 120 days, and white blood cells from a few days to years (Blood cell).

It can be hard to find other turnover times, but it ought to be evident that turnover rates can vary widely.

[RexT]

Right, so it's abundantly obvious to everyone that people change noticeably over time. We change in every conceivable way, as we could expect since everything changes. The only constant is change. Does the OP's question merely present this tautology as it seems, or does it yet conceal some profundity?

[Iblis waswas]

I'm curious, all the cells in the body have regenerated within whatever timescale, be it 10 or 20 years. Is there any explanation for how memories are retained? Do the collective of cells that hold our memories replicate and pass on these memories or do our brain cells not regenerate like the rest of our body?

[lpetrich]

The structures remain, even if their building blocks get replaced.

It's like owning a bicycle and gradually replacing piece after piece of it, including its frame (its central part; List of bicycle parts). The bicycle's structure continues, even if it has none of its original parts.

[Full Tilt Boogie]

It depends on what cell it is. e.g. blood cell, skin cell, stomach tissue cell

Recent studies have shown that few cells live as long as the individual they belong to without renewal. A majority, if not all, the cells making up the cerebral cortex belong to this small group. The life span of some other human cells are as follows:


Lifespan of select human cells:

Cell Type -- Lifespan
•Granulocytes -- 10 hours to 3 days
•Stomach lining cells -- 2 days
•Sperm cells -- 2-3 days
•Stomach lining cells -- 2 days
•Colon cells -- 3-4 days
•Epithelia of small intestine -- 1 week or less
•Platelets -- 10 days
•Skin epidermal cells -- 2 - 4 weeks
•Lymphocytes -- 2 months - a year
•Red blood cells -- 4 months
•Stomach lining cells -- 2 days
•Macrophages -- months - years
•Endothelial cells -- months - years
•Pancreas cells -- 1 year or more
•Bone Cells -- 25 - 30 years

A good example is blood cells at any given time the cells in your blood range from minutes old to 3-4 months but the above should give you some idea. I have put a link below for you to look at.

http://en.wikipedia.org/wiki/Red_blood_cell

[Rie]

Oh stuff and nonsense! I am not the same person as I was 20 years ago. The world has changed and the naive but hopeful me of 20 years ago has gone. To be replaced along with ye renewal or demise of grey cells with a brand new grievingness at mistakes made and time wasted.

[Berthold]

Is it not the case that brain cells (neurones) do not regenerate?
Even if they are old as cells: the molecules that build the shape are exchanged (well, most of them; DNA is an exception).

[toker]

Disambiguate the word 'same'. I fly the same flag as my neighbor. This morning I put on the same shirt I wore yesterday.

Two flags, one shirt. Type vs instance. Similar vs identical.

You're the 'same' instance of a person as you were yesterday (20 yrs ago). You are not the 'same' type, though, since you've changed so much.