Today's primarily mathematically oriented arbitrage theory does not address some economicallyimportant aspects of pricing. These are, rst, the implicit conjecture that thereis \the" price of a portfolio, second, the exact formulation of no{arbitrage, price reproduction,and positivity of the pricing rule under short selling constraints, third, the explicitassumption of a nonnegative riskless interest rate, and fourth, the connection between arbitragetheory (that is almost universal pricing theory) and special pricing theories. Ourarticle proposes the following answers to the above issues...