oxygen caused fire. So this is the fundamental problem of causal effect or observing certain things by observing certain other things and trying to link them. So what I arguethat this is really fundamentally what scientific methods are all about. You take observations, then you formulate a hypothesis, and then you test it, and then you refine it. So now if you were 5,000 years ago, then how do you know that oxygen is not causing the fire? What do you have to do? This is where this idea of necessary sufficient conditions become extremely problematic. In this particular case, now you know that, like for example, in my room right time I'm sitting here there is oxygen but there is no fire so that means why is not there so you may see oxygen is necessary but not sufficient what is sufficient then you need to have some trigger. If you have a trigger, then it will start fire. See, you know, start basically put some fire here with a maybe with a candle or something that makes me, my house may get into fire. So there's the distinction we need to make say but this is right now may seem very obvious but when you get into the messiness of say transboundary water management or other complex problems there are many many causes can create an outcome. Many many causes can create something that you see. So fire, there's what you see. Then you try to attribute some cause. And then you get into this idea of necessary and sufficient conditions. What we are arguing really in complexity that no, in complexity problems or the problems which are complex where many