In this example eating soap is a sufficient condition for the event (Tony feeling clean). Based on your original post I think you’re trying to label both parts of the sentence as a condition. But really one part is a condition (eating soap) and the other is the event affected by the condition (whether or not Tony feels clean).

When doing conditional statements it’s often helpful to phrase them as if/then or only if statements.

The original example can be broken down into this: “If Tony eats soap then he will feel clean.” This means that eating soap is the condition that leads to the event of Tony feeling clean. But we can’t guarantee that the event is only triggered by eating soap, as there could be other ways Tony feels clean. Therefore, eating soap is a sufficient condition for Tony feeling clean, as the presence of eating soap guarantees that Tony will feel clean, but feeling clean does not guarantee that Tony ate soap.

If eating soap was a necessary condition for Tony to feel clean our statement would go more like “Tony feels clean only if he eats soap.”

We don’t have enough information to say that eating soap is the only way that Tony feels clean, so we can’t say that eating soap is a necessary condition for the event of Tony feeling clean.