For thousands of years, long before there was such a thing as a science of chemistry, people were fascinated by plants, because they knew that plants contained substances that could affect people. Coffee will keep you awake. Tobacco contains something that will calm your nerves. Foxglove contains an extract that'll affect your heart.
When I wrote 'The Giver,' it contained no so-called 'bad words.' It was set, after all, in a mythical, futuristic, and Utopian society. Not only was there no poverty, divorce, racism, sexism, pollution, or violence in the world of 'The Giver'; there was also careful attention paid to language: to its fluency, precision, and power.