Actually I think a larger quote from Eistenstein may be of value here in explaining the “why”:
"Gesell's phrase, "... a monstrous hallucination, the doctrine of 'value'..." hints at another effect of demurrage—it makes us question the notion of “value.” Value assigns to each object in the world a number. It associates an abstraction, changeless and independent, with that which always changes and that exists in relationship to all else. It is part of humanity's descent into representation, the reduction of the world into a data set. Demurrage reverses this thinking and removes an important boundary between the human realm and the natural realm. When money is no longer preferred to goods, we will lose the habit of defining a thing by how much it is worth.
Whereas interest promotes the discounting of future cash flows, demurrage encourages long-term thinking. In present-day accounting, a forest that has the capacity to generate one million dollars a year every year into the foreseeable future is considered more valuable if immediately cut down for a profit of 50 million dollars. (The net present value of the sustainable forest calculated at a discount rate of 5% is only $20 million.) This state of affairs results in the infamously short-sighted behavior of corporations that sacrifice (even their own) long-term well-being for the short-term results of the fiscal quarter. Such behavior is perfectly rational in an interest-based economy, but in a demurrage system, pure self-interest would dictate that the forest be preserved. No longer would greed motivate the robbing of the future for the benefit of the present. The exponential discounting of future cash flows implies the "cashing in" of the entire earth as opposed to an immediate wholesale “liquidation” of our remaining resources.
Whereas interest tends to concentrate wealth, demurrage promotes its distribution. In any economy with a specialization of labor beyond the family level, human beings need to perform exchanges in order to thrive. Both interest and demurrage represent a fee for the use of money, but the key difference is that in the former system, the fee accrues to those who already have money, while in the latter system it is levied upon them. Wealth comes with a high maintenance cost, thereby recreating the dynamics that governed hunter-gatherer attitudes toward accumulations of possessions.
Whereas security in an interest-based system comes from accumulating money, in a demurrage system it comes from having productive channels through which to direct it – that is, to become a nexus of the flow of wealth and not a point for its accumulation. In other words, it puts the focus on relationships, not on "having". The demurrage system accords with a different sense of self, affirmed not by enclosing more and more of the world within the confines of me and mine, but by developing and deepening relationships with others. It encourages reciprocation, sharing, and the rapid circulation of wealth.
In today's system, it is much better to have a thousand dollars than it is for ten people to owe you a hundred dollars. In a demurrage system the opposite is true. Since money decays with time, if I have some money I'm not using right now, I am happy to lend it to you, just as if I had more bread than I could eat, I would give you some. If I need some in the future, I can call in my obligations or create new ones with anyone within my network who has more money than he or she needs to meet immediate needs. As Gesell put it:
With the introduction of Free-Money, money has been reduced to the rank of umbrellas; friends and acquaintances assist each other mutually as a matter of course with loans of money. No one keeps, or can keep, reserves of money, since money is under compulsion to circulate. But just because no one can form reserves of money, no reserves are needed. For the circulation of money is regular and uninterrupted.
No longer would money be a scarce commodity, hoarded and kept away from others; rather it would tend to circulate at the maximum possible "velocity". The issuer would ensure stable prices (P) according to the equation of exchange (MV=PQ) by regulating the amount of currency in circulation (M) to correspond to total real economic output (Q). The same result could be achieved by linking the currency to a basket of commodities whose level corresponds to overall economic activity, as proposed by Bernard Lietaer.
The dynamics of a demurrage-based currency system ensure a sufficient amount for all. This is in contradiction to today's economy in which a surfeit of material goods is coupled with their grossly unequal distribution. Hence the deeper contradiction in which, on the one hand, there are hundreds of millions of people who are unemployed or engaged in trivial, meaningless jobs, while on the other hand there is much important, meaningful work left undone—highlighting a disconnect between human creativity and human needs. "With Free-Money demand is inseparable from money, it is no longer a manifestation of the will of the possessors of money. Free-Money is not the instrument of demand, but demand itself, demand materialized and meeting, on an equal footing, supply, which always was, and remains, something material."
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