Today I want to share with you guys a graphic I often draw for my students who are having trouble conceptualizing the difference between a sufficient condition and a necessary condition. In my tutoring, I like to use clear-cut, everyday examples to illustrate and simplify the more complex concepts we are dealing with on the LSAT, and this is one I have found helps a lot of people.

The sufficient condition is the “if” in an “if-then.” If I use an umbrella, I will stay dry. I don’t have to have an umbrella– I could stay dry some other way– but the umbrella would do the job for me.

The necessary condition is the “then” in an “if-then.” If I am to sit in the chair, then I must have that chair leg in place.” That leg doesn’t guarantee I could sit in the chair– if that’s the only leg I have, I will still fall on the ground. But I have to have it.

These concepts are fundamental to understanding conditional logic in both logic games and logical reasoning. In future blog posts, I will explore the ways they come up!