When I used to write about IQ (general intelligence) differences between groups, I found that there were two basic assumptions towards the topic.
Either someone accepts the spontaneous impression - supported by what-appears-to-be vast amounts of consistent evidence - that general intelligence differs between groups;
or else they assume that all groups are of equal intelligence.
If someone accepts that groups differ in intelligence then this can be used as a basis to explore the concept of intelligence, measure it, discover what influences it - and so on.
But if someone assume that all groups are of equal intelligence then they need to explain-away what they regard as misleading data - what indeed (given their assumption that in reality all groups are of equal intelligence) must be misleading evidence.
And the explaining-away process operates by suggesting one after another alternative explanation, until attention is exhausted or time runs-out.
So... IQ differences between groups are explained-away by attacking the concept of intelligence. Or suggesting that it is not completely free from problems.
But if the concept is convincingly defended, and no superior alternative hypothesis can be devised, then often the alternative explanation of personality differences is proposed.
So IQ differences are explained-away as being really down to personality differences.
But when it tuns out that personality differences are much the same as IQ differences (being similarly stable throughout life, and heritable) then personality differences must be explained-away - for instance in terms of childhood upbringing.
But how to explain differences in childhood upbringing?
Well differences in upbringing turn-out to have rather similar distributions and (from the point of view of defending an assumption of equality) the same kind of problems as both IQ and personality - so differences in childhood upbringing must be explained-away - say, in terms of, say, economic differences.
But how to account for economic differences, if you are not allowed to explain them in terms of intelligence, personality or prior upbringing?
Well... perhaps in terms of evil.
Economic inequality is a product of selfishness, let's say.
But how to account for the unequal distribution of selfishness - why are the economic-haves so much more selfish than the economic have-nots?
(Recalling that differences in selfishness cannot be explained in terms of IQ, personality, upbringing or economics? - all of which have been explained-away.)
Well, perhaps selfishness differences (and/ or economic factors) can be explained-away in terms of culture - some cultures, once established, have specific socio-political or ethical systems in relation to selfishness, or specific types of economies, which lead to everything else...
Yes, okay, but what about the differences between cultures?
The terminus of this debate can only come when the ultimate explanation is found to be random, sheer luck.
In explaining-away and explaining-away any departures from an observable state of equality between groups, the only stopping point is luck.
(Luck of climate, geography, the random acts of natural disasters, random differences in the effects of disease... whatever).
And furthermore it must be assumed that random chance is self-perpetuating - because repeated acts of pure chance would tend to equalize, not polarize - so there must be first luck and then some kind of intrinsic tendency for the unequal operations of chance to be sustained and amplified.
So, everything is down to randomness, and the tendency that random differences are self-perpetuating. What of it?
If the assumption of equality is to be sustained then luck must be regarded as an unacceptable reason for group differences, at best non-moral - but in practice luck must be regarded as immoral.
It must be regarded as morally wrong that some cultures have more luck than others.
Indeed this is the bottom line for assumptions of equality - luck is immoral.
According to this line of argument, since luck is immoral, therefore people must be equalized, to compensate them for the unfairness of bad luck.
(And the process of equalization must be impersonal, machine-like, algorithmic - in practice bureaucratic.)
I don't know - because (please try to follow this!) if it is (merely) our our culture that tells us that it is not right for luck to generate inequality, and culture is (merely) a matter of chance, then this moral principle (that random chance is evil) has zero traction.
That same morality which tells us that luck is unfair is itself (merely) a matter of chance.
In explaining-away apparent inequality of intelligence, you have explained-away any morality which might regard inequality of intelligence as undesirable.
So, by logical steps we reach a bottom line of nihilism in which nothing matters because nothing is real.
Sorry, I have momentarily forgotten; what was it we were trying to explain-away?
Oh yes, the apparent differences in intelligence between groups...
On the other hand, what if the spontaneously apparent differences in IQ between groups is real?
Just assume this, for a moment, for the sake of argument.
Errr... no problem with that.
No infinite regress opening-up with that assumption.
End of discussion.