The law of diminishing marginal utility is an economic concept that states that as a person consumes more and more units of a particular good or service, the satisfaction or utility derived from each additional unit decreases. In other words, the more we consume of a particular good, the less value or satisfaction we derive from each additional unit.

According to Marshall, the law of diminishing marginal utility applies on all commodities except money. This means that the concept of diminishing marginal utility is applicable to goods and services, but not to money. Let's understand why this is the case.

**Diminishing Marginal Utility and Goods:**
When we consume goods or services, we experience diminishing marginal utility. For example, suppose you are hungry and you eat a slice of pizza. The first slice of pizza will satisfy your hunger to a great extent, giving you a high level of utility. However, as you consume more slices of pizza, the level of satisfaction or utility derived from each additional slice will decrease. Eventually, you may reach a point where you are full and consuming additional slices of pizza will provide very little or no satisfaction at all.

This concept applies to almost all goods and services. As we consume more and more of a particular good, the additional utility derived from each unit decreases. For instance, the first ice cream cone may bring great joy, but the tenth one may not be as enjoyable.

**Money and Diminishing Marginal Utility:**
On the other hand, Marshall argued that the concept of diminishing marginal utility does not apply to money in the same manner as it applies to goods. Money is a unique commodity that serves as a medium of exchange and a store of value. Unlike goods, money does not provide direct satisfaction or utility. Instead, money enables us to acquire goods and services that provide us with utility.

The utility derived from money is not related to the quantity of money possessed; it is related to the goods and services that can be obtained with that money. As we accumulate more money, the utility derived from each additional unit of money remains constant because money itself does not provide direct satisfaction. It is the goods and services that money can buy that provide utility, and the diminishing marginal utility concept applies to those goods and services, not to money itself.

**Conclusion:**
In conclusion, Marshall's argument that the law of diminishing marginal utility applies to all commodities except money suggests that the concept of diminishing marginal utility is applicable to goods and services, but not to money. Money does not provide direct satisfaction or utility; it is the goods and services that can be obtained with money that provide utility. Therefore, the law of diminishing marginal utility applies to goods and services, while money behaves differently in terms of utility.