"They say a little knowledge is a dangerous thing, but it's not one half so bad as a lot of ignorance"

This quote by Terry Pratchett is a suggestion that expertise is power. Having a little understanding can be dangerous, as it can bring about overconfidence and rash choices. Nonetheless, having a lot of ignorance can be even more dangerous, as it can result in an absence of understanding as well as an inability to make educated choices. Pratchett is recommending that it is better to have some understanding than none in all, as it can help to stop mistakes and negative choices. He is also warning versus the dangers of having too much expertise, as it can bring about arrogance and a lack of humbleness. Ultimately, Pratchett is advocating for a balance between expertise as well as lack of knowledge, as this is the best means to make informed decisions and avoid harmful errors.