Necessary/Sufficient 2

Necessary is something that must occur for the second act to follow (but does not guarantee that Act 2 will occur).

For example, it is necessary to put food into your mouth before you can eat. You can't eat without first putting food into your mouth.

So in general, when you have a statement that expresses a necessary condition, it allows you to infer something in just two cases:

1. You can infer from knowing that if the necessary condition is not met that the thing it is the necessary condition for does not occur.

- If you don't buy a Powerball ticket, then you won't win the Powerball jackpot.

2. You can infer that the necessary condition is met from knowing that the thing it is the necessary condition for occurs.

- If you won the Powerball jackpot, then it means you bought a Powerball ticket.

Sufficient is something that guarantees that the second act follows.

Rain is sufficient to make the sidewalk wet.

If the sidewalk is dry then you know it didn't rain.

So in general, when you have a statement that expresses a sufficient condition, it allows you to infer something in just two cases:

1. If you know that the sufficient condition is met, then you can infer that the thing it is the sufficient condition for occurs

2. You can infer that the sufficient condition is not met from knowing that the thing it is the sufficient condition for does not occur