Correlation vs. Causation

Statements like smoking and  lung cancer have a correlation are hardly controversial anymore. Enough research on this topic has be done to be confident that there is a correlation between smoking and and increased likelihood of getting lung cancer. Other examples of obvious correlation would be overweight people and their diet/ lifestyle or  not brushing ones teeth and getting cavities. As one can see there is a correlation between those things and it doesn't matter which way the correlation goes but with causation this is very different. Even though it might seem obvious that smoking causes lung cancer, a bad diet leads to overweight and not brushing your teeth leads to cavities and therefore smoking is the causation for lung cancer bad diets the causation for overweight and so on it might be possible that people that have an increased likelihood for lung cancer just tend to get addicted to smoking or that peoples overweight causes them to eat fast food. Even though this examples are ridiculed it shows how it does not matter in which direction correlation goes but it does matter in what direction causation goes and it can be very hard to tell which even causes the other at times.