Man is the measure of all things. So sayeth Protagoras, ancient scientist. If you're the religious kind you might condemn Protagoras for idolatry, for only God has the measure of all things. Or if you're William Blake, you might condemn Isaac Newton for succeeding at the task.
Before we get to Newton and Blake, let me make an important distinction between two kinds of measurements:
Objective measurements. These are measurements of entities out there in the real world, where despite the possibility of error, there's an underlying quantity being measured. My height is an example of an objective quantity; you will measure my height wrong if you have the wrong tape measure and I might add a couple of inches to it while creating a profile on a dating site, but we can all agree that there's such a quantity as my height.
Measurements of Exchange. Money is the best example. Let's say I want to appear taller than I am and I go out to buy a pair of platform shoes. How much should you charge me? Should a man 5'4'' pay the same amount of money to add 2'' to his height as a 5'6' tall man? If now, who should you charge more? Height's objective, the increase in height is objective, but the money you charge for it isn't objective. The measurement of exchange value is variable by design.
The measurement of objective quantities is closely tied to precision calculations and mechanization. I better measure the distance between my landing gear and the ground if I want my spaceship to land gently on the Moon's surface instead of crashing into it. The flip side of precision is a dismissal of quantities that can't be measured accurately.
Perhaps they don't even exist!
In contrast, the measurement of exchangeable commodities is tied to assessments of value. Why does gold cost more than iron? Objective explanations only go so far. Is it scarcity? Not really, because my childhood drawings are scarcer and I bet you won't pay any money for them. Is it because gold is hyper malleable and a good conductor? I am sure that plays a role, but advertisements have beautiful women wearing gold necklaces rather than highlighting the conductance of gold wires.
Exchange value can never be reduced to objective quantity.
That's my reading of Blake, i.e., that measurement leaves out what's most important about us. Perhaps, but there's good reason to try measuring the most obdurate phenomena.
Most people living in modern societies work for money. How to value their labor? It's a real challenge, for strictly speaking, we are trying to compare apples and oranges. Material inputs and labor go in and widgets come out. Labor is nothing like the widgets it produces, but yet there must be a way to turn widget numbers into wages for labor, for without that conversion, we have no way of keeping the factory going.
If our factory is a cooperative, we might say:
we produced X widgets that are sold at Y dollars each;
it cost us Z dollars to buy the inputs and maintain the equipment and we need to carry another W dollars for future investments, insurance etc.
Since there are A of us, we will each get (XY-Z-W)/A.
That seems relatively easy. But what if there's one owner and A employees. How much should the owner get and how much should the employees? Should they be paid a fixed salary and let all the profits go to the owner? If so, why?
What's the value of labor? What's a fair wage? We don't have unique answers to these questions because the measurement of exchange can't be reduced to the measurement of objective quantities. However, we have to live with an uneasy merger of facts and values because the alternative is even worse. To understand why, let's explore that age old question:
Can money buy me love?
One of the universal myths of the modern world is that subjective qualities, emotions in particular, are immeasurable in both senses of that term, i.e.,
there's no objective way of getting to my feelings and
there's no price to be put on them.
In fact, so powerful is the myth that love's immeasurable that it sparked one of the most successful pricing campaigns in the history of modern advertising. Some relationships and feelings are beyond the reach of the accountant, but for everything else there's:
The immeasurability of love reveals itself in all three sectors of human relationships:
Why does A fall in love with B? The myth comes with an answer: chemistry, "love at first sight." Of course there's something special about catching the eye of a person across a room and feeling a knot in your stomach when they look back with doubled energy. But who is likely to evoke that zing in the first place?
If you take romance novels as your guide, the answer is pretty clear: love on first sight is a lot easier if the other person is a born aristocrat with charming manners and the flawless skin that comes from a worry-less life. Money may not be able to buy love directly, but it sure tilts the scales in favor of the rich. In that, love is a lot like "merit," where entrance to Ivy League schools is theoretically open to the deserving of all races and classes but in practice favors the graduates of Phillips Andover.
The romance of familial relations is equally suspect. A mother's love is supposed to be infinite and unquantifiable but in practice it means that women labor long hours to keep a family going without compensation. How can you charge for the immeasurable?
Even friendship isn't immune to the pressures of the market, for we treat friends differently based on how much money they have. There's a reason why Drona was deeply offended when Drupada treated him like a servant. It's much easier to raise money for my next startup if I am rich and my friends are rich and they know even richer people.
My point is that the lack of measurement often leads to injustices of value. Every parent of multiple children has been told at some point or the other that he loves child A more than child B. But what does more love mean exactly? If I say I love my children equally and you (i.e., one of my children) say that I love Jimmy more than I love you, how exactly can we resolve this problem? There isn't a final answer to this question, but we can all agree it's unfair if I will 80% of my wealth to Jimmy and only 20% to you for no other reason than I love him more.
All of this would be moot if love simply can't be measured, but this is where abstract philosophical and scientific questions about the theory of measurement meet changing technological resources.
Until recently, emotion measurement was a rare affair. I knew how you were feeling only when I saw you or heard about you from a common friend. Aggregate data didn't exist - there was no way even the richest advertiser could have gauged the feelings of her customers on a daily basis.
All of that has changed dramatically. We reveal our emotional states to platform companies and governments several times a day, perhaps several hundred times a day. As a consequence, they have excellent models of our emotional state and wellbeing. Instagram and Snapchat probably knows when my daughter is going to have a fight with one of her friends even before she does.
That degree of access to emotions is clearly worth money and it's reflected in the valuation of Facebook and other corporations. In fact, whether money buys love or not, it's been able to buy hate at scale - and the electoral fortunes of Trump, Bolsonaro and Modi are testament to that success. The only way to counter that wave of hatred is if the measurement of love expands at a faster rate than the measurement of anger and if emotions more generally are made into a public resource rather than the property of private corporations.