Axiom:Sure-Thing Axiom

Axiom
The sure-thing axiom states that:

If a rational decision-maker $P$ would prefer:
 * option $1$ over option $2$ when event $A$ occurs

and:
 * option $1$ over option $2$ when event $A$ does not occur

then $P$ would prefer option $1$ over option $2$ in absence of any information about the occurrence or not of event $A$.