As a utilitarian and small-d democrat, I will concede right away that if people really want inequality, then we should have as much inequality as we really do want. However, part of my argument is that a lot of people do not actually want inequality; I suspect that people at the bottom of the distribution tolerate inequality because they believe it is objectively moral or that equality is physically impossible. Furthermore, utilitarianism entails that society changes because people change what they want, and I want to change what people want.
Before I begin the actual argument, I want to state again what I do and do not mean by strict equality. Strict equality means that each person, under all circumstances, receives an equal share, by some metric of "equal", of the social product.
I do not, however, mean that everyone receives exactly the same bundle of goods: 2 lbs of chicken, 17 tomatoes, 2 board games, etc. People have different preferences, and will consume different bundles of goods. I also do not mean that everyone must work the same amount and receive the same amount of stuff: leisure is part of the social product, and people can choose to trade off stuff for leisure. I am also talking only about equality of demand on the social economic product; I am not talking about equality of physical characteristics or capabilities, social status, admiration and prestige, or anything else like that. I'm arguing only for equal access to the goods and services we produce as a society.
Finally, I understand that I cannot simply wave a magic want and implement strict income equality. Similarly, I am not arguing about a particular method of implementing strict income equality. A minority of people overthrowing the government by force of arms and imposing strict income equality on the citizenry by force would be a Very Bad Idea. However, there are a lot of other ways to move society materially towards strict equality.
Essentially, I want to argue that we should move towards strict equality, and we should move there by intentionally and deliberately decreasing inequality directly, rather than ignoring the problem and hoping other, more "fundamental" changes will deliver equality indirectly.
My argument will (hopefully) include the following points (I'll add links when I flesh them out, and otherwise adjust the summary as I think of new points or abandon old ones):
- Economic argument: Declining marginal utility of income; consumption as a zero-sum game.
- A perfect, ideal world would have strict income equality.
- Strict income equality is entailed by the ideal of "free markets."
- Income inequality is undemocratic.
Counterarguments and rebuttals:
- Access to medical care could be unequal; people who receive a lot of the social product in the form of medical care should not have to trade off access to other stuff. Concede: this form of "inequality" will probably be the last to go.
- There is utilitarian value for income inequality today. Concede, but argue we can and should change present inequality; present inequality poses a technical problem, not a fundamental problem.
- There is a non-utilitarian, deontic case ("just deserts") for inequality. Rebut by arguing that deontic morality is incoherent in general, and terrible when applied to access to the social product.
- Utilitarianism is incoherent. Rebut by arguing utilitarianism is coherent.
- Strict income equality is less efficient. Partially concede — so what? — but fundamentally rebut: argue strict income equality is more efficient than inequality.
- Strict income equality is a million years away. Rebut by arguing it's feasible soon.
- Humans are naturally competitive. Weakly concede, but we can compete over things (e.g. prestige) other than the social product.
If you want to suggest other arguments or raise counter-arguments, please do so in the comments.