Working on distributive justice issues, one of the most salient theoretical distinctions between conceptions is the question of which currency of justice a theory uses. Here a whole range of currencies have been proposed by different philosophers from welfare, utility, basic goods, basic needs, capabilities, (in climate justice, even carbon emissions) etc.
As of course every discipline wants to be relevant, one could question why—as everything nowadays is expressed in monetary terms—philosophers don’t use money as their currency of justice. This would facilitate real life application of philosophical theories and make them more comparable to economic and other social science theories that use money as their basis.
Some reasons why philosophers tend to use other currencies than money is that they believe that money is only a proxy for other values and/or that certain values cannot at all or at least not be easily translated into monetary terms. Further certain values might be incommensurable and therefore not possibly be expressed in monetary terms.
I, for my dissertation, follow Amartya Sen’s and Martha Nussbaum’s capability approach. Both thinkers were not satisfied with accounts that focused on basic goods (or other kinds of resources). For one thing, in their opinion, such accounts were missing the fact that people often need different amounts of resources to achieve similar functionings. They therefore proposed the currency of capabilities (to functionings), which aim to measure substantive freedoms (what a person is able to do and be), rather than measure the resources a person has. The capability theory is also critical of utilitarian theories that use currencies like well-being. As those theories aim at measuring satisfied preferences, they claim that such currencies have a problem dealing with adaptive preferences (some persons lower their expectations and so don’t claim what they ought to), they are also critical of utilitarianisms focus on mental states.
Depending on the currency, distributions can take very different shapes, such as when we talk about finding a fair distribution to divide a cake. Take the example of a cake. A resource egalitarian might slice the cake into same-size pieces. A needs theorist might distribute slices depending on how much cake every person needs to be nourished. A utilitarian would distribute the cake so the most happiness (or preference satisfaction) would be created.
So that’s why philosophers do not use money as a currency of justice. Using different currencies, philosophical theories take a much more detailed look at what is valuable in a person’s life and on how that relates to other values. Still, we are far away from a general agreement on which is the optimal currency of justice that should be used.
But if you ask me … of course the right currency are capabilities. More on that next time!
 For example when it comes to health a capabilitarian would argue that a person should have the capability to lead a healthy life, meaning that the person has the opportunity to live a healthy life by, among others, having access to health care, being able to healthily nourish herself, being aware of how to lead a healthy life. What is important is the freedom to lead a healthy life not the actual functioning (meaning the realisation of the possibility that the freedom gives) because which capabilities a person realizes in the form of functionings is the free choice of individuals.