Non-Satiation Axiom
The non-satiation axiom is a core principle in consumer theory. It states that, all else being equal, a rational consumer will always prefer a bundle that contains a greater quantity of at least one good. In other words, more is always better. This axiom is typically illustrated using a Cartesian diagram with parallel indifference curves.
In the diagram, bundles A and B contain the same amount of good X2 (bread). However, bundle B includes a larger quantity of good X1 (apples). Given the choice, and assuming no other changes, a rational consumer will prefer bundle B because it offers more of good X1 without reducing the amount of good X2. The same reasoning applies when comparing bundle A with bundle C. In both cases, bundles B and C are preferred to A because they offer more of one good without any trade-off in the other. The additional quantity of goods in bundles B and C yields a higher level of satisfaction, as measured by the utility function.
Preference for Higher Indifference Curves. The non-satiation axiom also underpins the consumer's preference for indifference curves that lie further from the origin. The outer indifference curve I2 corresponds to a higher consumption level of at least one good, holding the others constant, and therefore represents a higher utility level than the inner curve I1.
Why It's Called “Non-Satiation”. The term “non-satiation” reflects the idea that a satiated consumer - one who has no desire for additional quantities - would no longer favor bundles that offer more. In such cases, bundles located on higher indifference curves (i.e., with more of at least one good) would cease to be preferred.
