Posted on 08/13/2005 12:26:50 PM PDT by beavus
...The book begins with a discussion of the medical use of embryonic tissue and the debate over whether a blastocyst (which is a ball of a few hundred cells) is a person. This section is thoughtful, clearheaded and informed by developmental neuroscience. One fallacy Gazzaniga exposes depends on the common idea that graded differences block principled legal distinctions. In the version referred to as the fallacy of the beard, the logic goes like this: If we cannot say how long a man's whiskers must be to qualify as a beard, we cannot distinguish between a bearded man and a clean-shaven one. Although this form of argument fools nobody on the topic of beards, it has been seductively employed elsewhere, especially regarding embryos. Criticizing the blastocyst-as-baby argument, Gazzaniga sensibly points out that we can draw a reasonable, if imperfect, line. When a distinction is needed, we devise laws that draw one, typically erring on the side of caution, given prevailing community attitudes. There is no precise moment at which a child becomes an adult, or a blastocyst becomes a sentient person, but reasonable humans unencumbered by superstition can nonetheless come together to "draw a line," and we can redraw the line when the facts merit a revision. Eighteen as the age of majority is not the perfect line for all adolescents, but on the whole it works well enough....
(Excerpt) Read more at americanscientist.org ...
For the same reason, there is no "precise moment" at which conception occurs. We see the world, and it changes smoothly.
Of course you could use the pragmatic approach described and just arbitrarily draw the line somewhere during the process of conception (I'm assuming you want the law to protect human embryos). Afterall, the author does say that the lines the law draws should be "typically erring on the side of caution". I guess it depends upon what margin of error is acceptable, eh?
Agree. This article should be aborted.
When that single 'lucky' spermatozoon breaches the ovum's membrane and the ovum immediately renders its membrane impervious to penetration by additional spermatazoa, conception has occurred. The fact that we almost never see that very rapid event occurring doesn't change the fact that it does occur.
Actually it is merely a simple matter of observational fact that no clear transition point exists. The transition from gametes to zygote is, of course, a smooth one.
I'm not sure I understand you here. If you are saying that the process of conception does occur, then of course I agree that is true, and it is as much a matter of observation as the fact that there is no precise time point dividing gametes from zygote.
...there is no precise time point dividing gametes from zygote.
I'm saying that there's an extremely brief time interval (not moment or instant) during which conception occurs; before that interval begins, one may say with confidence that conception has not occurred and after it one may with confidence say that conception has occurred. There is a well-defined chemical change in the membrane of an ovum after a single spermatozoon has penetrated it, which change prevents other spermatozoa from penetrating the membrane. Before that change occurs, sperm and egg are distinct, after it occurs, the single fertilizing sperm and egg begin their fusion dance.
Naturally, this interval of time, while extremely brief, is not an 'instant' (i.e., a mathematical point of time). But it's not clear that 'nature at an instant' has any actual meaning anyway. No physical measurement of which we're aware is capable of recording an interval of time shorter than the Planck time, which is approximately 10-43 seconds, and, of course, we're nowhere near being able to measure so short an interval. But the chemical interactions which take place in biological cells are of much longer duration, anyway.
But we're probably not disagreeing. It's probably just this 'precise moment' terminology that's getting in the way.
You told me you could tell within a week. Close enough.
Yes, the conclusion that: therefore you can't know when life begins is quite false.
Yes, that is right. Sorry I doubted you, but there are people on this forum willing to chop off your left foot in defense of the "scientific fact" that a precise dividing time exists. In fact, you are quite a rarity in my experience.
But it's not clear that 'nature at an instant' has any actual meaning anyway. No physical measurement of which we're aware is capable of recording an interval of time shorter than the Planck time, which is approximately 10-43 seconds, and, of course, we're nowhere near being able to measure so short an interval.
Maybe, but the continuum doesn't require real-number-line kind of smoothness. The fallacy of the beard (when describerd as plucking hairs one by one) is a good example of a continuum of discrete intervals. Our current technology is resolute enough to see that there is no sharp division in the life cycle, because we can see short enough intervals to know that no two adjacent time points at our best resolution are significantly different.
Actually, it is KNOWN that there is NO time point when life begins.
Yes, this is key. We are in agreement.
...the continuum doesn't require real-number-line kind of smoothness...
I prefer to reserve the term 'continuum' for sets of cardinality of the real numbers (or larger). But that's just my math background speaking. I understand what you mean.
Yes, we're in agreement.
Can we change Democrats' values by injecting them with Republicans' stem cells?
"Continuum" has a broader sense then "the continuum" or aleph0. This is fortunate, since the mathematical concept of infinite sets is unnecessarily complicated for conveying to ordinary folks the facts of observed natural continua.
Since I've explained my point to you at length in many ways with multiple analogies, you are going to have to be more specific.
My immediate point is just that your statement indicates you have a misunderstanding of reality.
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