Necessary conditions are conditions which must be fulfilled in order for an event to come about. It is impossible for an event to occur unless the necessary conditions for it are fulfilled. For example, a necessary condition of you passing your A-level Critical Thinking is that you enrol on the course. Without doing so, there’s no way that you can get the qualification.

Sufficient conditions are conditions which, if fulfilled, guarantee that an event will come to pass. It is impossible for an event not to occur if the sufficient conditions for it are fulfilled. For example, a sufficient condition of you passing AS Critical Thinking is that you get enough marks on the two exams. If you do that, there’s no way that you can fail.

Some arguments confuse necessary and sufficient conditions. Such arguments fail to prove their conclusions.

Example

“People who don’t practice regularly always fail music exams. I’ve practiced regularly though, so I’ll be all right.”

Not having practiced regularly may be a sufficient condition for failing a music exam, but it isn’t necessary. People who have practiced regularly may fail anyway, due to nerves, perhaps, or simply a lack of talent.

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