In chapter 4, "The Value of Life and the Value of Death", Weikart writes p. 73:
One of the alluring features of Darwinism, it seems to me, was that it offered a secular answer to the problem of evil and death. Indeed, it was more than an answer - it gave Darwinists hope and inspiration that suffering and death would ultimately spawn progress.
Ending that same paragraph, Weikart writes:
In one respect, then, Darwin's theory of natural selection was a secular answer to Judeo-Christian theodicy (the justification of a benevolent God in a world of evil), since it provided an explanation for the existence of evil and promised that evil would ultimately fulfill a good purpose.
I see no reason to disagree with Weikart here. However, on p. 75, Weikart writes:
The Darwinian idea of death as a natural engine of evolutionary progress represented a radical shift from the Christian conception of death as an unnatural, evil foe to be conquered. This shift would bring in its train a whole complex of ideas that would alter ways of thinking about killing and the "right to life." Before Darwinism burst onto the scene in the mid-nineteenth century, the idea of the sanctity of human life was dominant in European thought and law (though, as with all ethical principles, not always followed in practice).
Is it as simple as that? The creationist Edward Blyth had in the 1830s written about natural selection as a mechanism that weeded out the defective individuals, those who deviated from the species. As such a mechanism to conserve the species, though he admitted for some evolution, a species splitting into varieties. Another creationist, Patrick Matthew, had in an appendix to his book On Naval Timber and Arboriculture from 1831 suggested that to improve timber quality, the trees of poor quality should be eliminated. He also wrote:
There is a law universal in nature, tending to render every reproductive being the best possible suited to its condition that its kind, or organized matter, is susceptible of, which appears intended to model the physical and mental or instinctive powers to their highest perfection and to continue them so. This law sustains the lion in his strength, the hare in her swiftness, and the fox in his wiles. As nature, in all her modifications of life, has a power of increase far beyond what is needed to supply the place of what falls by Time's decay, those individuals who possess not the requisite strength, swiftness, hardihood, or cunning, fall prematurely without reproducing - either a prey to their natural devourers, or sinking under disease, generally induced by want of nourishment, their place being occupied by the more perfect of their own kind, who are pressing on the means of subsistence ...
Yes, like Darwin, Matthew was inspired by Thomas Malthus. Still, the idea of eliminating the sub-standard to keep the standard was alreday there. Darwin's addition was that natural selection could even improve a species, which of course, species being created perfect, would be an odd idea for a creationist mind.
Another mental leap was, of course, seeing humans, not as specially created, but having evolved from animals and therefore subject to the same natural laws as animals. However, Darwin's The Origin of Species did not deal with humans, and The Descent of Man didn't recommend more brutal methods for eugenics than forbidding consanguineous marriages and recommending to the inferior that they should not marry. Consanguineous marriages are also forbiden in Mosaic law, and we also have this interesting little piece from Genesis 38:
6 And Judah took a wife for Er his firstborn, whose name was Tamar.
7 And Er, Judah's firstborn, was wicked in the sight of the LORD; and the LORD slew him.
That is, Er was wicked ('re' in Hebrew) and was killed for that reason, before he could get any children. Isn't this eugenics? True, it was God ("the LORD"), who killed Er; but it doesn't take much to get the idea that God has appointed you as his instrument for killing off the wicked.
On p. 77, Weikart writes:
[August] Forel explained to Haeckel that in his view monism is the "scientific proof of the essential identity of the psychological activities of humans and their neurophysiological side." By undercutting the Judeo-Christian and Kantian claim that humans had unique moral status based on an immaterial soul, Haeckel, Forel, and other Darwinists helped undermine the idea that human life is intrinsically sacred and inviolable.
Why? If humans have an immaterial soul, obviously human physical life is not necessarily sacred. Strictly speaking, the sooner physical life was terminated, the sooner would the soul be able to go to heaven.
On p. 78, Weikart writes:
The Darwinian worldview, according to [Robby] Kossmann, subordinated the individual to the community, since all individuals necessarily perish - indeed myriads die before reproducing - but the species continues. This means that the value of an individual's life can only be measured by its contribution to the welfare of the community.
"Ask not what your country can do for you, but what you can do for your country," as the saying goes in God's chosen nation.
On p. 79, Weikart writes:
Eugenicists, for example, often compared the selective breeding of animals, which they saw as rational and scientific, with human reproduction, which seemed irrational and arbitrary. The clear implication was that humans would be better off if they would treat each other the way they treat animals, at least in the area of reproduction. Sex was thus reduced to a mere biological function.
Oh, dear! In the article The Second Tablet Project, J. Budziszewski, who happens to also be a DI-CSC fellow, writes:
A theist who attributes the order of nature to God can say things like this: "I see that the sexual powers cause conception, and that the fact that they do so is part of the explanation of why human nature has been endowed with such powers in the first place. This tells me that conception is a purpose of the sexual powers, a part of what they are for. When I employ them, I ought to respect this fact; I ought not to use them in ways that are incompatible with their purpose."
However, Budziszewski claims that a Darwinist would think differently. For Budziszewski, sex is also a mere biological function, though designed by God. For a theist, the purpose of sex is to cause conception; for a Darwinist, the purpose of sex is to cause conception. What is the difference?
AiG president Ken Ham writes in the article The relevance of creation, when writing about clothes:
What we should say is this - there is a moral basis for wearing clothes, because of what sin does to nakedness. We must understand how men are created, that they were designed to be easily aroused sexually and respond to one woman this [sic] wife, and this was and is necessary for procreation in marriage.
Also for Ham, who is certainly no Darwinist, sex is only a question of procreation, and men are even particularly designed to be easily sexually aroused.
In chapter 5, "The Specter of Inferiority: Devaluing the Disabled and 'Unproductive'", Weikart writes p. 90:
Haeckel regularly marshaled Darwinian arguments in support of inegalitarianism. In The Natural History of Creation (1868) he explained thatbetween the most highly developed animal soul and the least developed human soul there exists only a small quantitative, but no qualitative difference, and that this difference is much less, than the difference between the lowest and the highest human souls, or as the difference between the highest and lowest animal souls.
It may be hard for us today to imagine that a serious scientist could actually believe that the differences within the human species are greater than the differences between humans and other animals, but this was indeed Haeckel's position, which he reiterated in many publications.
And now we all thought that Haeckel had done away with the soul! Exactly, what Haeckel is implying in the quoted passage isn't easy to figure out. Anyway, Weikart clearly gets the wrong impression. Haeckel does not compare humans to other animals en bloc. At worst/best, he states that some humans are closer to some animals than other humans, and that some animals are closer to some humans than other animals.