Eugenics is “the study of, or belief in, the possibility of improving the qualities of the human species or a human population by such means as discouraging reproduction by persons having genetic defects or presumed to have inheritable undesirable traits (negative eugenics) or encouraging reproduction by persons presumed to have inheritable desirable traits (positive eugenics).”
The above definition, provided by the Random House Dictionary, is adequate in many respects but fails to acknowledge a series of important elements that the eugenicists themselves believed about their belief system. In particular, eugenicists themselves incorporated three other important ingredients, usually quite explicitly. First of all, they did not see their view as a ‘study’ of something, but rather a science in itself. Secondly, and not by any means less important than the first example, they saw the endeavor as relying on Darwinian principles of evolution. Thirdly, they saw their science as one that deliberately brought to bear the realities concerning human biology to the social sphere, and in particular to the areas where entities—the State being a prominent example—had the ability to influence human biology through “social agencies under [their] control.”
These elements are obscured in large part because everyone associates the Nazis with eugenics. People tend to be wholly unaware that the British and Americans were equal to the Nazis in their eugenic efforts. Hitler possessed what these other eugenicists greatly coveted: the authoritarian system in which to enforce their various schemes. As authors Jackson and Weidman say, “Popular understanding of eugenics is often restricted to the horrors of Nazi Germany, but, in fact, leftists proclaimed their adherence to eugenic doctrines as much as those on the political right.”
How particular groups “applied biology” in their particular countries were varied, but what they all had in common was the biology. Jackson and Weidman call attention to the scientific and social elements that united diverse ideologies in their application of evolutionary principles: “[E]ugenic thinking was a way to think about social problems in scientific terms.”
Modern definitions and understandings of ‘eugenics’ diverge in important ways from how the eugenicists themselves understood the concept. The material below will help set the record straight.
Historically, there were several competing definitions. The man who coined the word in the first place was Sir Francis Galton, the cousin of Charles Darwin. Galton first uses it in his 1883 book, Human Faculty, and describes the process by which he settled on the word:
That is, with questions bearing on what is termed in Greek, eugenes namely, good in stock, hereditarily endowed with noble qualities. This, and the allied words, eugeneia, etc., are equally applicable to men, brutes, and plants. We greatly want a brief word to express the science of improving stock, which is by no means confined to questions of judicious mating, but which, especially in the case of man, takes cognisance of all influences that tend in however remote a degree to give to the more suitable races or strains of blood a better chance of prevailing speedily over the less suitable than they otherwise would have had. The word eugenics would sufficiently express the idea; it is at least a neater word and a more generalised one than viriculture which I once ventured to use.
In 1904, he read aloud a paper that was subsequently published in The American Journal of Sociology titled, “Eugenics: It’s Definition, Scope, and Aims.” In this paper, Galton offers this more refined definition:
Eugenics is the science which deals with all influences that improve the inborn qualities of a race; also with those that develop them to the utmost advantage. 
In the papers of the Third International Conference on Eugenics, this definition by Galton is provided in the front matter:
Eugenics is the study of the agencies under social control that may improve or impair the racial qualities of future generations either physically or mentally.
Galton was seen as an authority on the concept and said, “Eugenics is officially defined in the Minutes of the University of London as ‘the study of agencies under social control that may improve or impair the racial qualities of future generations, either physically or mentally.'”
Other definitions of the period include “Eugenics is the self-direction of human evolution” which was on the logo for the Second International Conference on Eugenics, reproduced below.
Charles Davenport, a prominent American eugenicist, stated that “Eugenics is the science of the improvement of the human race by better breeding.”
Paul Lombardo, addressing the shifting definitions of ‘eugenics’ said:
First, in practice—as it played out in law and social policy—the definition of eugenics was always changing. To some it meant cutting the tax burden generated by welfare dependent mothers by preventing the birth of more children of poverty. To others, it meant encouraging the most prosperous and successful to multiply, while impeding the replication of the deviant, the disabled, the diseased, or the criminal. Still others used eugenics as a touchstone for their fears that “inferior” racial groups were growing and must be interrupted lest they overrun a less fertile but “superior” race.
One doesn’t always find straightforward definitions of the term. Often, it is descriptive instead. Such descriptions illustrate that there were various ingredients essential to the understanding of the word that do not always come out in the definition of the word.
To understand the ideological impetus behind eugenics, one must understand the chain of reasoning that links three essential components. This can be understood most simply by charting this reasoning and the three components as employed in Leonard Darwin’s Presidential Address to the First International Conference of Eugenics. (Leonard Darwin was one of Charles Darwin’s sons.)
First, he grounds their efforts on the laws of nature: “A belief in evolution merely implies a belief that all changes which have taken place and which are taking place in this world are changes in which effects follow causes in accordance with unvarying laws.”
Then we find that he sees eugenics as the study between the interplay between the “unvarying laws” of biology and society. “We must have a bridge to unite the domain of science with the domain of human action, and such a bridge forms an essential part of the structure of Eugenics.” Indeed, his invoking of Galton’s definition of eugenics zeroes in on the social application of biological principles. He says, “Eugenics, as Sir Francis Galton termed the study of agencies under social control that may improve or impair the racial qualities of future generations, presents, it was stated, problems of the utmost social importance.”
But eugenics is not just a bridge between science and society, which L. Darwin finally makes clear: “To endeavor both to study the laws of heredity and practically to apply the knowledge thus acquired to the regulation of our lives, seems, therefore, to be a paramount duty which we owe to posterity.”
This third and final element, this sense of ‘duty’, provides the necessary moral imperative, the sense that one ought to bridge science and society, that one ought to apply the “unvarying laws” of evolution to society, that motivated eugenicists to action.
On this definition, many readers may very well conclude that on this basis, they are eugenicists. Setting aside this troubling implication, the readers may very well wonder why it is that their own beliefs do not threaten humanity to the same extent that eugenics ultimately did. (We may very well wonder if even that is true!) The missing ingredient is the eugenic belief that this sense of ‘duty’ did not have an individual component, but a societal component. That is to say, for the eugenicist, a higher kind of moral law applies to society that does not apply to the individual. The individual should act in the interests of the race, but the race has the right and duty to put the interests of the race above the interests of the individual, even if this means the trampling of the ‘rights’ of certain individuals, or even their elimination.
The spirit of this view is well-illustrated by various references to the ‘social organism‘ and equating it with the state or race. For example, American geneticist Leonard Cole (out of the University of Madison, WI) wrote approvingly of this illustration:
Death is the normal process of elimination in the social organism, and we might carry the figure a step further and say that in prolonging the lives of defectives we are tampering with the functioning of the social kidneys!
To glimpse that this wasn’t mere metaphor, but an actual operating principle, consider the use of the same analogy by Karl Binding and Alfred Hoche, the authors of Allowing the Destruction of Life Unworthy of Life, the German book that laid the intellectual and ethical grounds for the Holocaust itself:
Seen from the point of view of a higher civil morality, there is no doubt that exaggerations are being exercised in the striving for the absolute preservation of unworthy life. We have learned, from someone else’s point of view, to consider in this respect the state organism as a whole with its own laws and rights, in the same way as, for instance, it would be for a self-contained human organism, which, as us doctors know, surrenders and rejects individual parts or particles that have become worthless or damaged in the interest of the well-being of the whole. 9pg 37)
Just as individual humans have mechanisms for eliminating waste, such as by defecating, so too does the state. Binding and Hoche do not shy away from the implications:
There was a time, which we now view as barbaric, in which the disposal of those born with unlivable conditions was considered natural, and then came the still on-going phase, in which the preservation of any whatsoever worthless existence is ultimately considered the highest moral requirement; there will be a new age, which, from the point of view of a higher morality, will stop making heavy sacrifices on the basis of an exaggerated concept of humanity and an over-protection of the value of mere existence. (pg 42-43)
With the eugenicists themselves thinking this way about Eugenics, it is important that our understanding of what constituted ‘eugenics’ according to actual eugenicists takes pains to incorporate these other elements. That is, if we are to pretend to draw lessons from the past, we must understand exactly what the people who erred in the past actually believed. It is clear that an “essential part” of eugenics was the belief that science should be brought to bear on society; duty to posterity demands it, and a ‘higher kind of moral law’ applies that can properly dispose of the ‘excrement’ within the ‘social body.’ 
It is critical to understand that Darwinism provided the critical, essential, instrumental, apparatus for eugenics. Not all Darwinists were eugenicists (although most were) but all eugenicists were Darwinists. The Darwinian component of eugenics is often waved off, as though it merely fed into a pre-existing racist outlook. The eugenicists did not see it that way at all. They perceived that their ‘racism’ was grounded on science, not prejudice, and eugenics the logical implication for the scientific-minded.
For example, after giving his definition of eugenics, Frederic Houssay, professor of science at Paris University, in his paper submitted to the First International Eugenics Conference, after considering sterilization as a viable means to eliminating defectives, said:
We see that the views here expressed fall into line with Darwinian theory, and it seems that by the simple application of the principles which follow from them, the group of defectives, considered at a given moment, could be rapidly extinguished, and that society thus cleansed could for a long period pursue a life of lessened burden and better health.
Having now incorporated more of what the eugenicists themselves thought ‘eugenics’ consisted of, here perhaps is a better definition of eugenics:
Eugenics: a scientific program seen to follow logically from the acceptance of Darwinian evolution and a moral duty to apply those principles to society with the aim of progressively improving it and the species.
This is not far from Houssay’s definition, which was “the social application of the science of biology.” Modern readers, however, would fail to see the significance of his invoking of the phrase ‘science of biology,’ not realizing it is pregnant with explicitly Darwinian principles. As his definition, and his understanding of the underlying lattice supporting the concept explicitly are Darwinian, the phrase ‘science of biology’ has been exploded in order to explain to modern readers more precisely what the eugenicists actually meant when they spoke.
Finally, contemporary discussions on this topic often use the phrase ‘social Darwinism.’ The phrase is often used interchangeably with the word ‘eugenics.’ There are definitely similarities, and the differences not enough to object to using them interchangeably, though there arguably are differences. This essay was limited to discussing the the word ‘eugenics’ rather than the phrase ‘social Darwinism.’ The former might be hard to define comprehensibly, but at least eugenicists are on record defining it for us. What constitutes ‘social Darwinism,’ on the other hand, is often in the eye of the beholder.
Underscoring this ambiguity as well as the continuing importance of the topic in general, historian of evolution, Peter J. Bowler, writing about the term and topic, “The whole subject generates endless controversy, the arguments being all the more heated because they bear upon issues still relevant today.”
Other definitions or variations of definitions of ‘eugenics’ entertained by eugenicists:
“… eugenics; that is, from systematic inquiry as to the transmittal of inborn and acquired traits from generation to generation, with a view to the possibilities of selection and breeding.” Frank Taussig, Principles of Economics, Volume II, 1911. Pages 233-237.
“… eugenics, which Galton defines as ‘the science of being well born.'” Herbert E Walter in an essay called “Human Conservation” found on page 473 of Readings in Evolution, compiled by Horatio Hackett Newman. First published in 1921.
“All racial progress, or eugenics, therefore, depends on the creation of a good environment, and the fitting of the race to that environment.” Paul Popenoe and Roswell H. Johnson in an essay called “Eugenics and Euthenics” found on page 495 of Readings in Evolution, compiled by Horatio Hackett Newman. First published in 1921.
“For centuries and even millennia, man worked to improve the breeds of his domesticated animals and plants. In stark contrast, the genetic endowment of mankind itself has been neglected almost entirely. Eugenics is an applied science aiming to end this neglect. Eugenics was defined by Galton, in 1883, as ‘The study of agencies under social control that may improve or impair the racial qualities of future generations either physically or mentally.’ Today we would use the word ‘genetic’ in place of Galton’s ‘racial.'” Theodosius Dobzhansky, The Future of Human Heredity: An Introduction to Eugenics in Modern Society (1968), v.
“Eugenics is concerned with the changes which may be taking place in human heredity. In more scientific language, it is concerned with the frequency and distribution of different types of genetic factors in successive generations of human populations. Essentially eugenics seeks to understand and ultimately to direct the forces that control human inheritance through matings, births, and deaths.
The idea of eugenics derived from Darwin’s theory of evolution, first established in The Origin of Species. If man is the product of a long evolutionary process, there is every reason to believe that man in his present form is only at a certain stage in his development, and still subject to change.” Frederick Osborn, The Future of Human Heredity: An Introduction to Eugenics in Modern Society (1968), 1-2.
 eugenics. Dictionary.com. Dictionary.com Unabridged. Random House, Inc. http://dictionary.reference.com/browse/eugenics (accessed: March 04, 2014).
 John P. Jackson, Jr., and Nadine M. Weidman, Race, Racism and Science: Social Impact and Interaction.(New Brunswick: Rutgers University Press, 2006), 109.
 The reader may think that this is an allusion to a prominent Nazi official’s statement that “National Socialism is applied biology” but this is actually how the eugenicists themselves saw their work. For example, Leonard Darwin, in a paper submitted to the Second International Conference on Eugenics referred to biology and genetics as “the pure sciences on which the applied science of eugenics is based.” See Eugenics, Genetics, and the Family: Scientific Papers of the Second International Congress of Eugenics, 1921 (New York: Garland Publishing, 1985),
 Jackson and Weidman, 109.
5. Similarly, an evolutionist who was prominent enough to be selected to give testimony at the ‘Scopes Monkey Trial,’ Horatio Hackett Newman, edited a book entitled Readings on Evolution, Genetics, and Eugenics, explicitly linking all three. He intended the book to serve as a textbook. In the Preface, he lays out the plan for the book and explains that eugenics is included because it is “genetics as applied to human improvement.” See: Horatio Hackett Newman, Readings in Evolution, Genetics, and Eugenics (Chicago: The University of Chicago Press, 1921, Reprinted 1924), vii.
 Francis Galton, Inquiries into Human Faculty and Its Development (London: Macmillan and Co., 1883), 24-25.
 Francis Galton, “Eugenics: Its Definition, Scope, and Aims,” American Journal of Sociology, Vol. 10, No. 1 (July, 1904): 1, http://www.jstor.org/stable/2762125
 A Decade of Progress in Eugenics: Scientific Papers of the Third International Congress of Eugenics (Baltimore: The Williams & Wilkins Company, 1934), Front Matter.
 Francis Galton, Memories of My Life (London: Methuen & CO.,1908), 321.
 Wikipedia, “Eugenics.” http://en.wikipedia.org/wiki/Eugenics (accessed March 5, 2014). Image URL= http://en.wikipedia.org/wiki/File:Eugenics_congress_logo.png (accessed March 5, 2014).
 Charles Davenport, Heredity in Relation to Eugenics (New York, NY: Henry Holt and Company, 1911), 1 .
 Paul A. Lombardo, ed. A Century of Eugenics in America: from the Indiana Experiment to the Human Genome Era (Bioethics and the Humanities) (Bloomington, IN: Indiana University Press, 2011), 6-7.
 A phrase from Leonard Darwin’s Presidential Address at the First International Conference of Eugenics on page 2, alluding to the fact that at the time of the conference, it was impossible to know what the results of their labors would be, but that just as advances in understanding the laws of weather allowed meteorologists to make increasingly more reliable forecasts, so too would increased understanding of the ‘unvarying laws’ of evolution.
 L. Darwin, First Eugenics Congress, 1.
 Ibid., 6. Emphasis added.
 Ibid., 1.
 Ibid., 3.
 A recent Masters dissertation by Birgit Arnold submitted in May, 2013 is titled “Let us Make Perfect Children: The Rhetorical Concept of Obligation in Eugenics Movements” discusses not just the evolutionary component of eugenics, but the fact that people believed society ought to “make perfect children” if it was in society’s power to do so.
 The definition he gave was, “Eugenics, or the social application of the science of biology.” See page 158 of the Papers of the First International Congress.
 His paper was titled “Eugenics, Selection and the Origin of Defects.” See page 158 of the Papers of the First International Congress.
 Ibid., 160.
 Ibid., 158.
 Peter J. Bowler, Evolution: The History of an Idea. 25th ed. (Berkeley: University of California Press, 2009), 299.