Conditional attitudes are not the attitudes an agent is disposed to acquire
in event of learning that a condition holds. Rather they are the component
s of agents' current attitudes that derive from the consideration they give
to the possibility that the condition is true. Jeffrey's decision theory c
an be extended to include quantitative representation of the strength of th
ese components. A conditional desirability measure for degrees of condition
al desire is proposed and shown to imply that an agent's degrees of conditi
onal belief are conditional probabilities. Rational conditional preference
is axiomatised and by application of Bolker's representation theorem for ra
tional preferences it is shown that conditional preference rankings determi
ne the existence of probability and desirability measures that agree with t
hem. It is then proven that every conditional desirability function agrees
with an agent's conditional preferences and, under certain assumptions, eve
ry desirability function agreeing with an agent's conditional preferences i
s a conditional desirability function agreeing with her unconditional prefe
rences.