Depends on what you're interested in and your level of mathematical maturity. I assume you're interested in real-world, actually applied decision making rather

Depends on what you're interested in and your level of mathematical maturity. I assume you're interested in real-world, actually applied decision making rather than philosophical debates, right? Then you have to look for multicriteria decision making (MCDM) and multi-attribute utility theory (MAUT). Eisenführ/Weber/Langer: Rational Decision Making. Springer 2010. This is a good practical introduction in the standard methodology. Keeney/Raiffa: Decisions with Multiple Objectives: Preferences and Value Tradeoffs. Wiley & Sons 1976. This is an older work, but very good. It's mathematically more rigorous and important if you want to understand additive and multiplicative models. Both of them are practical and give good examples. The first one is easier to read. If you're not afraid of more complicated mathematics, I can also give you some more other references. I guess you wouldn't be asking me then, however, because there is plenty of sources. I generally recommend Peter C. Fishburn's work, insofar as I can understand it -- some of it is too hard for me.