Is there any decision that can't be restated as an arbitrarily complicated series of if/then statements? If you're patient, you can do addition using just if-th

Is there any decision that can't be restated as an arbitrarily complicated series of if/then statements? If you're patient, you can do addition using just if-thens (IF N1 = 1 and N2 = 5 THEN answer = 6), etc.