Most people know what side effects are. They are the results of something a person does, or of a medication that a person takes, or perhaps a decision a person makes; and these results are either unnecessary, or unwanted, or sometimes even counter to the effect the person was going for. But there is really no such thing as a side effect. There are only effects, which can be helpful, neutral, or harmful. Therefore the question becomes whether all the effects can be known, and whether the helpful effects are worth the cost of the harmful ones.