## Monday, December 13, 2010

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About a year ago we have discussed at length the problem posed here; it is one of the stock objections against the potentiality argument. The intuition behind the objection is this. Suppose you have a chain of causes c1…cn. Then if you attribute a potentiality property to any element in the chain, say ci, then (i) it makes sense to drive that potentiality property all the way back to the initial element of the chain; and (ii) there is no natural cutoff point cj in the chain of causes such that subsequent to cj it makes sense to attribute the potentiality property, whereas prior to cj it makes no sense to apply the potentiality property.

When we last examined this problem, someone (I forgot whom) introduced the notion of ‘developmental potential’. I take it that the intuition behind development potential was this: certain causal chains have a *natural segment* such that there is a first link in the natural segment which constitutes the beginning of the development and that this first link is the cutoff point so that any potentiality property that is attributed to any subsequent point can be driven back through the causal chain only to the initial link and no further.

I think that this intuition is fundamentally correct. Many children have the potential to become great mathematicians, musicians, or basketball players. But it simply makes no sense to say that some particular sperm or unfertilized egg has any of these potentials. How far back can we drive this potential through the causal chain? I am not sure that I have a conclusive answer! But if pressed, I would venture the following answer.

A sub-section of a causal chain constitutes a *natural segment* provided there is at least one individuating property P such that: (a) the initial link of the natural segment features P; (b) if any link n subsequent to the initial link in the natural segment features P, then link n+1 features P; and (c) no other entity outside the natural segment features P.

Let the DNA of a given fetus be P. Then I think that the DNA defines a natural segment with the fertilization of the egg constituting the initial element. Hence, developmental potentialities can be driven back only up to this point and no further.

Of course, I do not insist that DNA is the only individuating property that can serve as defining the cutoff point. But the conditions specified above require at least one such property and DNA will do in many cases. So if personhood is a developmental property, which I think it is, then it can serve as a developmental potential. And so the property of being a potential person can be only driven back to a certain point in the causal chain and no further (perhaps to the point of conception).

By the way, Peter, Tony Hanson responds to you in the earlier abortion thread. More later!

Peter,

I agree with you. If an entity has an essence and its potentiality is constrained by that essence, would you say that "developmental potential" is essence in naturalistic terms?

Regards,
Bill T

John,

The Combox is open or not on a post-by-post basis.

I am glad to have you as a reader! And Tingley too.

Merry Xmas,

Bill

Merry Christmas to you and yours, Bill.

Bill T

Dear Peter,

I think you have captured my intuition quite clearly, thank you. However, I do not think DNA is a suitable candidate for an individuating property. Your third condition, (c), is "no other entity outside the natural segment features P". But DNA is not unique to a single entity so it does not fulfil this condition. Identical twins, both of which had the same zygote in the chain of causes that led to their development, share the same DNA. (There is also a non-zero probability that any two people drawn from the same population have the same DNA.)

If an individuating property that truly defines a "natural segment" could be found, then that might provide good grounds to reject proposition (ii): "there is no natural cutoff point cj in the chain of causes such that subsequent to cj it makes sense to attribute the potentiality property, whereas prior to cj it makes no sense to apply the potentiality property."

If DNA is not such a property, what is? Unless such a property is identified, I think it is reasonable to accept (ii).

Dear Bill,

I am sorry I have taken so long to comment on this post. Work and Christmas have not left me much time for pleasant pondering. However, I now have a few days off around New Year so I shall take the opportunity to respond.

You wrote, "I also disagree when you say that the "potential develops gradually along with the entity.""

I was attempting to convey my hunch that thinking in terms of Aristotelian/Thomistic potentiality may not be helpful in this situation. Actualization of potentiality requires that we already have an entity with a certain potentiality that might be actualized as the entity develops. However, the problem in this situation is that we are trying to determine when that entity comes into existence.

We both agree that the entity possessing P cannot possibly be in existence before conception. I fully agree that it is "spectacularly obvious that there are things that have a potentiality-to-X that their constituents, taken individually, do not have". However, I do not agree that it is obvious that conception is the moment when an entity possessing P comes into existence. I think it is quite plausible that it comes into existence at some point after conception.

In your dough analogy, you said, "The potential is had only by the ingredients when properly mixed." The trick is to work out which part of the human embryological process is analogous to the dough's being "properly mixed". It is tempting to choose conception because it superficially appears to be the stage at which all the "ingredients" have been "mixed" into a single blob. However, I contend that this is a false analogy. Your December 16th post, Fission and Zygotes [1], provides one example of a way in which human fertilization and development is different from merely mixing dough ingredients.

For reasons of "moral safety" it may well be best to take conception as a cut-off point. However, I do not think you have a compelling argument that conception really is a rational cut-off point. To use the terminology of Peter Lupu's comment, it is necessary to identify some individuating property that defines a "natural segment". So far, I have not seen any such property identified. Embryology just isn't enough like cooking to make the analogy of mixing ingredients hold up.

Happy New Year!

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