The Black Widow spider example doesn't seem particularly problematic to me, as the male spider passes his genes on when he fertilizes the female, and since he has no further role to play in raising the offspring, he has no further evolutionary purpose (except as protein).

i think homosexuality poses a far more interesting obstacle to evolutionary theory, if you're looking for a problem to home in on.  i disagree that the very concept of evolutionary motives is unfalsifiable.  If you accept the theory (for the sake of argument) there are some explanations which are very clearly in line with it and others which are much less obvious - not necessarily false, but certainly requiring evidentiary support.  There are some things which are difficult to explain from an evolutionary point of view, i have no problem with admitting that.  My suggestion to EB was simply that it would be hugely debate-enhancing if he actually addressed the specific weaknesses of an individual evolutionary explanation, rather than forgoing the intellectual effort in favour of banal negative generalisations.

i think there are what we might call second order principles (from my point of view) in play here, and that "sanctity of life" might be one of them.

As a heuristic rule-of-thumb, valuing the "sanctity of life" (whatever that precisely means) is probably mostly a positive thing for the wellbeing of society.  However, it can be applied outside the framework of wellbeing and suffering (in the abortion debate, for example), which i would consider to be a mis-application of an otherwise useful heuristic principle.

Suppose space aliens came to Earth with the same general intelligence level as humans, but very different in their physical characteristics.  But morality-wise, I think we'd want to say they translate as "human."

i suspect that EB and SJ would disagree with that, given that they consider "human-ness" to be paramount, which extraterrestrials would be unlikely to share.  i guess on that basis ET could be tortured to death without a single moral qualm - unless wellbeing and suffering is somehow independently diagnostic of morality, as i would suggest.

Your phrasing suggests that you consider homosexuality to be "immoral", but what objective principle does it violate?

Huh, you're knowledgable about animals' precise inner motivations now are you?  How do you know they don't have a care for anything else?  Could it be you pre-existing beliefs?

Of course you would.  You wouldn't stoop to anything so menial as providing evidence or supporting arguments for your disbelief in primate self-awareness, but since it contradicts your belief system you are happy enough to dispute it without engaging any of your higher faculties.

Pick'n'mix definitions to suit the occasion.  Clearly the Duck-Billed Platypus is not an animal by your definition, since it is really very different from any other animal.  When you say "unique" you actually mean "human" (question-begging restrictions apply).  i'm not really too motivated to carry on hacking away at your impenetrable wall of certainty, now that there are more reasonable people around.

A couple of thoughts in response to this - spiders lay lots of eggs (to be more precise, several hundred each time they reproduce), although many of the offspring may not survive.  This is an approach to reproduction which we might call the scattergun technique, in contrast to the mammalian thing of investing a proportionally far larger amount of energy and effort into a very small number of offspring.  But in either scenario, you could argue that it would benefit the gender which expends less energy in the process to reproduce again, but that assumes that the male (in this case) has a choice.  Black widow spiders are strongly sexually dimorphic, with the male being about half the size of the female.  So while you may be quite right that it is not in the male's interests to be eaten after sex, it is in the female's interests to eat him, and she is probably quite difficult to argue with.  Evolutionary strategies don't always have to benefit both genders equally.

I'm still not sure it isn't possible to always come up with an evolutionary-sounding explanation if one is creative enough.  But I'm not a scientist and certainly not a biologist--perhaps you can give me an example of something that clearly contradicts the whole evolutionary motive thing?

Isn't that akin to asking me to give you an example of something that effectively disproves evolutionary theory?  If i knew of something like that then my beliefs would be rather different.

i am sure that, at a minimum, speculative evolutionary explanations can be advanced for all existing biological phenomena,

but that is only an argument for the unfalsifiability of evolutionary theory if evolutionary theory is false (and is not the same as saying that an evolutionary explanation could be concocted for any imaginable biological process).  If evolutionary theory is true, then evolutionary explanations do exist for the whole gamut of diverse life on this planet, and those that are speculative only are so because of the difficulty of providing empirical evidence for prehistorical events.

My first order principles are worth, equality, and proportionality, so perhaps one could say sanctity of life is a second order principle under that framework.  But so is well-being.

It's possible that we're recreating the famous historical battle over the chronological primacy of the chicken vs the egg here.

Human worth flows from the fact that humans are made in God's image, unlike other animals (but some animals may well be closer to that image than others, and that may be something that informs our treatment of them).  But space aliens may also be made in God's image.  If they are, then for moral purposes, they translate as "human" even if they are physically unlike humans.

Oh come on!  Are you seriously suggesting that if aliens landed in Kentucky then we would be conducting some sort of arcane tests to determine whether or not they were also made in God's image before we decided whether to treat them as objects of moral concern or not?    The deciding factor would surely be whether they had the capacity to experience mental states similar to ours, in terms of wellbeing and suffering.

As a thought experiment, let's imagine that we go to them, rather than them coming to us.  That takes out the complicating factor of the level of technological/intellectual sophistication necessary to navigate interstellar space.  Let's say that our first manned mission to Mars finds complex life forms (as unlikely as that may be) - social tool-using creatures with obvious likes, dislikes and emotions, living in family groups, with certain observable strict codes of conduct - what process would we go through to decide whether they were worthy of moral concern?

Because we live within the categories set by our less-knowledgable ancestors, it is hard to see that if we suddenly discovered chimpanzees in the 21st Century (it may have been obvious that i was basing my nouveau-Martians on chimps) there would be little doubt that this was another sentient species, worthy of full human rights.  Because we are used to thinking of them as animals, we generally write off their examples of thoughtful and moral behaviour as unthinking instinct or (if you're really sophisticated) anthropomorphisation by primatologists.  i am personally happy to defer to the actual experts over the "armchair-primatologists" on this issue.

Also, if there is a continuum of "being made in God's image" in the animal kingdom, does it have any correlates with complexity and behaviour?

It might be interesting to take a population of black widow spiders and tweak some of the conditions which are thought to contribute to sexual cannibalism - availability of males, fertility of females, etc - to see whether the behaviour continues.  i suspect it would gradually be selected against, but it's tricky to reverse engineer these kind of strategies in order to deconstruct the precise evolutionary motives for them.  i'm trying not to assume my conclusion here, but i don't really see the issue.

Let's take an example then.  What if there was a sort of Lemming who fit the "mass suicide" myth about the species.  Whole communities which spontaneously hurled themselves off cliff-tops leaving behind only a few vulnerable newborns, to weak to defend themselves, to carry on the next generation.

i cannot conceive of any evolutionary explanation for such behaviour.  If it was observed, i think we would actually be asking "what is the environmental explanation for this?", thinking in terms of pesticide pollution or accumulation of heavy metals in the food chain making the furry little critters psychotically suicidal.

Not necessarily, i agree.  Theistic evolutionists might think that God intervened late in the process.  i would add that evolution giving rise to morality does not mean that all moral impulses will be obviously evolutionary in nature (since many people seem to think that an evolved morality would be entirely amoral).  i'm thinking of analogies to things like the antlers of a stag, or the peac*cks tail, which actively hinder the animal in its everyday life but which have developed as a means for the sexual signalling of "fitness", meaning that the larger they are, the more "tail" (haha) the possessor gets.  There is a balance of selection pressures, and in the same way, the moral principle against rape may seem anti-evolutionary from a man's point of view until we consider how likely we are to be excluded from the community that we depend on for survival if we dont obey it.

You didn't respond to my rat example, which I think constitutes some evidential support for the primacy of the principles of worth, equality, and proportionality with respect to morality.

Apologies, i didn't think it gave any greater primacy to worth over wellbeing.  i would say that we ascribe humans (or dogs) more "worth" than rats because we think that humans and dogs have a greater capacity to experience the mental states of wellbeing and suffering than rats. Likewise, we would prioritise a rat over a fly, and for the same reasons.  i think the example could support either position.

That makes it seem slightly arbitrary.  It is a kind of essentialism to suggest that there is an other-worldly quality which we cannot measure that alone conveys worth to creatures.  What is to stop someone claiming that a rock, or more topically, a book, also shares this quality of partaking in God's image to some extent.  People often engage in this kind of (unstated) essentialism with regards to their holy books, treating assaults or insults to them as being as bad or worse than if they were directed at a human.  Even assuming that such a means of deriving worth is true, i wouldn't find it especially useful to include it in moral calculations.  Surely better to invoke things which we can actually measure.

Of course we would have to look at their behavior, their capacity to experience mental states, etc.  If a space alien seems to be advanced in these respects (roughly as advanced as humans, less advanced but very close compared to native species on Earth, or more advanced), then we'd have to assume they are made in God's image.  Any uncertainty in that regard, should err on the side of that assumption.

Ok, those are things that we can at least attempt to quantify.  You seem perilously close to saying that the characteristic of being worthy of moral concern (whether or not that is framed as being made in god's image) is diagnosed by the capacity to experience wellbeing and suffering.

There are certainly some big differences.  Not really significant anatomical or physiological differences, but in the areas of cognition and lifestyle i agree.  But even in those areas there are some animals which are clearly closer to use than they are to the slug and the worm.  Don't you think?

So in a way, using that as a measure of intellect or worth would be culturally discrimination - like judging people on their command of the English language who didn't grow up speaking it.

"Also, if there is a continuum of "being made in God's image" in the animal kingdom, does it have any correlates with complexity and behaviour?"

Yes.

Then i would say it is more useful to frame the discussion in terms of those correlates, rather than metaphysical intangibles.  No offence.