What is valuable? What makes something good, or beautiful, or worthy of pursuit? Axiology is the philosophical study of value. It covers ethics, which concerns moral value, and aesthetics, which concerns aesthetic value. The term comes from the Greek axios, meaning worthy, and logos, meaning study. It entered philosophy in the late 19th century, as thinkers like Franz Brentano and Alexius Meinong tried to develop a general theory of value.

Axiology asks whether values are objective, subjective, or something in between. Are values discovered or created? Do they exist independently of human preferences? Intrinsic value is value something has for its own sake. Instrumental value is value something has as a means to something else. A diamond has instrumental value for its hardness and intrinsic value for its beauty, if you accept that beauty is intrinsic. Value pluralism holds that there are multiple irreducible kinds of value. Value monism holds that all value reduces to one kind, often pleasure or well-being.

Key distinctions

• Intrinsic vs. instrumental value. For its own sake vs. as a means.
• Objective vs. subjective value. Independent of minds vs. dependent on them.
• Moral vs. aesthetic value. Goodness vs. beauty.
• Monism vs. pluralism. One kind of value vs. many.

Axiology matters in practical fields like economics, where value is measured by price, and in policy, where competing values must be weighed.