The conditional claim is only one. So it can't be an entire argument. Necessary and Sufficient conditions Let's use an example to illustrate these concepts. If it is raining, then it is cloudy. First, the claim is true.
Rain comes from clouds.
Now sometimes it is sunny and raining. That's an unusual experience, but it happens. And the relationship works this way. Whenever the first condition is present, then the second condition MUST be present. In other words, that is all it takes to ensure the consequent.