There is evidence that suggests that aluminum is a neurotoxin. There is evidence that shows that glyphosate is a cause of infertility.
Many vegans contend that a plant-based diet is positively associated with healthy aging. 
There is a traditional Chinese belief that sweeping with a broom on New Year’s brings bad luck. But how do we know if these things are actually linked or if they are just randomly associated? How do public health officials, medical doctors, and the patients themselves determine if there is a cause-and-effect relationship between aluminum and brain decline or glyphosate and fertility challenges? 
This isn’t just a philosophical debate. Figuring out the answers to cause-and-effect questions has the potential to impact many of our health and lifestyle choices. …