1st Class = Positive – True
2nd Class = Negative – False
3rd Class = Neutral – Maybe
4th Class = Wish List

1st Class Conditional if = If and it is true

2nd Class Conditional if = If and it is not true

3rd Class Conditional if = If and maybe it is true or maybe it is not true

4th Class Conditional if = If and I wish it were true

Each class can be affected by various modifiers, especially the 3rd and 4th classes.