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Equality is a concept that is easy for humans to grasp, even when they are very young and have not learned to act outside of emotional impulse. Its understanding may either be motivated by jealousy of another, seeing that someone else has more, or conversely be taught via a hypothetical scenario which draws on the same motivation, ie, "how would you feel if someone else had more than you do?". These inauspicious beginnings aside, it is one of the fundamental, core issues in Ethics and one of the most profound advances for human society, enabling them to cast aside issues that would undermine it or destroy it.
Equality has been studied in the philosophical discipline of Egalitarianism
Egalitarianism has in turn been split, ultimately by those who wish to embrace one or more of its aspects without having to adhere to its whole, but in part by those who cannot beat that so instead join it, taking part in at least part of the discourse where they see a definition that is distinct and manageable.
The concept of equality has always been plagued to some degree by a fundamental dichotomy between two different focuses of the same word. Equality as a measure of what a person receives, and as a measure of their abilities. Obviously it is not equality to give two people different shares of a thing, but because it is possible to measure their achievements, this is used as justification for what is obviously unequal.
The measure of a human
Up to the 19th Century, rulers had always relied on Might Makes Right, a justification that they were superior in some way to those they ruled, to some extent. This was given additional impetus following the publication of Charles Darwin's Wikipedia:Descent of Man. Darwin's theories about Evolution were themselves a product of a hierarchical society, with a culture that recognized class and 'breeding', and were infused with just enough of that for it to be quite easy for his ideas to be subverted toward what has since been called Social Darwinism.
Capitalism, and in no small part capitalism after the Industrial Revolution (wherein reliable mass production of clocks established the measure of time as another measure of productivity) added another aspect to the dichotomy of 'equality': productivity was the measure of a human in the economy. The laziest members of the society, the ruling class (not only in sheer output of Ergs but most particularly in pay to work ratio), neatly sidestepped their own measurement system, relying on the perception that no one else could do the work they do; this worked particularly well as no one noticed its circular logic: anyone who was capable was immediately accepted as part of the ruling class, and on top of it all, they could pat themselves on the back for being so open and free as to allow new members.
Since then, it has been all the easier for those who extract value from others to tell the lies that pass for justification. The next step was divide and conquer, using a scary red herring: other humans with lower measures (less productivity) might steal value from you if all measures of humans were given equal value, eg equal pay. Nevermind that those who are really stealing are never counted, and at that point it is no longer your pay anyway, but granted at the pleasure of the employer. Or that everyone works the same hours, and tries pretty much as hard. Or that workers are at their most efficient when they are doing work they enjoy, so paying money as an incentive is ultimately self defeating, as people then only take jobs because of the money. Marx attempted to wake everyone up to the concept of capitalists stealing value, but he never seemed to notice they had themselves been left out of the value counting, and instead just attempted to say they did nothing, when obviously they do organizing. He never believed workers could organize themselves, and neither did the Russian communists, so they had to ignore the problem altogether. He never even bothered with the concept of equal pay itself, and obviously, neither did they. Half of the eager young people that have ever thought communism sounded like a really good idea must have gotten quite a shock when they found out that there were really poor communists (although never homeless or unemployed ones) and really really rich ones; I know I was. It was simultaneously a disappointment and a big joke: what was the US' big problem with Communism if they had a rich ruling class, anyway? Electoral college, single party, not that much difference between them, in the end. Getting people who can do highly skilled labor is never a problem; I have never for a second bought the idea that those with autonomous, powerful, challenging and interesting jobs, also needed to be paid more as an incentive. As Doonesbury said, of Democrats, "Sensitive to the plight of the working class? Of course, how else do they avoid belonging to it?"
- KG Work and society: a reader by Keith Grint, page 17
- The city in history: its origins, its transformations, and its prospects By Lewis Mumford page 104
- Technics and Civilization by Lewis Mumford, 1934, is also credited by many scholars as pertaining to this topic, but the book itself is not listed on Google Books at all, a sad and unusual occurrence
- Neither can Landes or his/er 1983 work, also cited by Keith Grint (see 'KG' cite) as pertaining, be found on Google Books