okay so real quick here's what the difference between a necessary and a sufficient condition is um now a lot of times in philosophy we have to ask the question what is X so what is a cat what is a Smurf or in the context of drug policy and the harm principle we're going to need to know what is it for something to be a harm because if we don't know what something is whether or not something is a harm we can't tell whether or not is covered by the by the harm principle so to be a necessary condition is to be a feature of that kind of thing which every one everything of that kind has so a necessary condition of being a Smurf is being blue because all Smurfs are blue if you find something that is not blue you know you don't have yourself Smurf if you got yourself Smurf you know you got yourself something blue on the other hand is sufficient condition is something that only members of that kind have so being blue is not a sufficient condition of being a Smurf because there's all sorts of other blue things out there that aren't themselves Smurfs um if it was a sufficient condition then anytime you ate a blueberry you'd be committing a horrible horrible crime against Smurf them and hopefully that's not the case so in short a necessary condition is something that every member of a Kind has but but other things can share too and a sufficient condition is something that only members of that kind have that can't be shared with anything else and the trick is there can be some things of that kind which don't have the sufficient condition but we don't really need to worry about that then finally there can be things that are both necessary and sufficient which is just you know putting a necessary condition together with the sufficient condition so this has an important implication for how we proceed if somebody's giving us a necessary condition for something that means that in order to test whether or not what they're telling us is true you have to look for something of that kind which does not have the necessary condition so if somebody said having four legs is a necessary condition of being a cat well then what we look for is a cat that does not have four legs and so poor Tippy or poor tripod would prove that that is in fact not a necessary condition if somebody is giving us a sufficient condition for something then the way we test it out is by looking for something that is not a thing of that kind but which has that property so if we said that having a tail is a sufficient condition of being a cat well we would show that that's false because plenty of other animals out there have tail koaa Bears dogs wombats at least I think wombats have tails fish all sorts of things have tails but are not themselves cats so having a tail cannot be a sufficient condition of being a cat