Since undergraduate courses in economics diminishing marginal utility law is a major paradigm. Indeed, quite of an intuitive concept: that is, “as a person increases consumption of a product while keeping consumption of other products constant, there is a decline in the marginal utility that person derives from consuming each additional unit of that product” (FreeDictionary.com). Translated, consuming increasingly more of a given good provides the individual with a gradually decreasing pleasure. Moreover, in the long run the utility given by consumption is zero and even negative. That is why, according to the marginalist theory, individuals differentiate their consumption among different goods (giving different levels of utility). The diminishing marginal utility law is based on practical and psychological assumptions. However, I’m wondering how and if this rule is actually determining human behaviours. One issue in economics is inequality of income, access to goods, services, etc.. Many times we read of or listened to economists and politicians reporting the huge gap between the richest and the poorest percentiles of the population. What’s the utility to a billionaire of having $1 million more? Close to zero, a marginalist, and I, would answer, yet I’m not so sure the billionaire would agree with us…what’s the economic failure – if this is the case – acting here? Is it an irrational impulse to greed, egoism, fear of loss, addiction to power? Then, how to correct this failure? Is redistribution the key tool? If so, why policy makers often escape from redistributive policies? Because of their ‘gratitude’ to the rich lobbies that have determined their political success, or of the expected future support? It seems to me that here collective and individual utilities are linked together and one’s utility determines the other’s. I don’t have any answer – maybe good questions? – and I won’t be surprised when a real economists will easily disclose how trivial is my logic. I warmly welcome theoretical references.